Txnip deletions and missense alleles prolong the survival of cones in a retinitis pigmentosa mouse model.

Retinitis pigmentosa (RP) is an inherited retinal disease in which there is a loss of cone-mediated daylight vision. As there are >100 disease genes, our goal is to preserve cone vision in a disease gene-agnostic manner. Previously we showed that overexpressing TXNIP, an α-arrestin protein, prolonged cone vision in RP mouse models, using an AAV to express it only in cones. Here, we expressed different alleles of Txnip in the retinal pigmented epithelium (RPE), a support layer for cones. Our goal was to learn more of TXNIP's structure-function relationships for cone survival, as well as determine the optimal cell type expression pattern for cone survival. The C-terminal half of TXNIP was found to be sufficient to remove GLUT1 from the cell surface, and improved RP cone survival, when expressed in the RPE, but not in cones. Knock-down of HSP90AB1, a TXNIP-interactor which regulates metabolism, improved the survival of cones alone and was additive for cone survival when combined with TXNIP. From these and other results, it is likely that TXNIP interacts with several proteins in the RPE to indirectly support cone survival, with some of these interactions different from those that lead to cone survival when expressed only in cones.

Dual Deletion of Keap1 and Rbpjκ Genes in Liver Leads to Hepatomegaly and Hypercholesterolemia.

The hepatic deletion of Rbpjκ (RbpjF/F::AlbCre) in the mouse leads to exhibition of the Alagille syndrome phenotype during early postnatal liver development with hyperlipidemia and cholestasis due to attenuated disruption of NOTCH signaling. Given the roles of NRF2 signaling in the regulation of lipid metabolism and bile ductal formation, it was anticipated that these symptoms could be alleviated by enhancing NRF2 signaling in the RbpjF/F::AlbCre mouse by hepatic deletion of Keap1 in compound Keap1F/F::RbpjF/F::AlbCre mice. Unexpectedly, these mice developed higher hepatic and plasma cholesterol levels with more severe cholestatic liver damage during the pre-weaning period than in the RbpjF/F::AlbCre mice. In addition, hypercholesterolemia and hepatic damage were sustained throughout the growth period unlike in the RbpjF/F::AlbCre mouse. These enhanced abnormalities in lipid metabolism appear to be due to NRF2-dependent changes in gene expression related to cholesterol synthetic and subsequent bile acid production pathways. Notably, the hepatic expression of Cyp1A7 and Abcb11 genes involved in bile acid homeostasis was significantly reduced in Keap1F/F::RbpjF/F::AlbCre compared to RbpjF/F::AlbCre mice. The accumulation of liver cholesterol and the weakened capacity for bile excretion during the 3 pre-weaning weeks in the Keap1F/F::RbpjF/F::AlbCre mice may aggravate hepatocellular damage level caused by both excessive cholesterol and residual bile acid toxicity in hepatocytes. These results indicate that a tuned balance of NOTCH and NRF2 signaling is of biological importance for early liver development after birth.

Carbonic Anhydrase 2 Deletion Delays the Growth of Kidney Cysts Whereas Foxi1 Deletion Completely Abrogates Cystogenesis in TSC.

Tuberous sclerosis complex (TSC) presents with renal cysts and benign tumors, which eventually lead to kidney failure. The factors promoting kidney cyst formation in TSC are poorly understood. Inactivation of carbonic anhydrase 2 (Car2) significantly reduced, whereas, deletion of Foxi1 completely abrogated the cyst burden in Tsc1 KO mice. In these studies, we contrasted the ontogeny of cyst burden in Tsc1/Car2 dKO mice vs. Tsc1/Foxi1 dKO mice. Compared to Tsc1 KO, the Tsc1/Car2 dKO mice showed few small cysts at 47 days of age. However, by 110 days, the kidneys showed frequent and large cysts with overwhelming numbers of A-intercalated cells in their linings. The magnitude of cyst burden in Tsc1/Car2 dKO mice correlated with the expression levels of Foxi1 and was proportional to mTORC1 activation. This is in stark contrast to Tsc1/Foxi1 dKO mice, which showed a remarkable absence of kidney cysts at both 47 and 110 days of age. RNA-seq data pointed to profound upregulation of Foxi1 and kidney-collecting duct-specific H+-ATPase subunits in 110-day-old Tsc1/Car2 dKO mice. We conclude that Car2 inactivation temporarily decreases the kidney cyst burden in Tsc1 KO mice but the cysts increase with advancing age, along with enhanced Foxi1 expression.

Development of a telomere vector-based approach to overcome limitations caused by lethal phenotypes in the study of essential genes in Magnaporthe oryzae.

Reverse genetic approaches are common tools in genomics for elucidating gene functions, involving techniques such as gene deletion followed by screening for aberrant phenotypes. If the generation of gene deletion mutants fails, the question arises whether the failure stems from technical issues or because the gene of interest (GOI) is essential, meaning that the deletion causes lethality. In this report, we introduce a novel method for assessing gene essentiality using the phytopathogenic ascomycete Magnaporthe oryzae. The method is based on the observation that telomere vectors are lost in transformants during cultivation without selection pressure. We tested the hypothesis that essential genes can be identified in deletion mutants co-transformed with a telomere vector. The M. oryzae gene MoPKC, described in literature as essential, was chosen as GOI. Using CRISPR/Cas9 technology transformants with deleted GOI were generated and backed up by a telomere vector carrying a copy of the GOI and conferring fenhexamid resistance. Transformants in which the GOI deletion in the genome was not successful lost the telomere vector on media without fenhexamid. In contrast, transformants with confirmed GOI deletion retained the telomere vector even in absence of fenhexamid selection. In the latter case, the maintenance of the telomere indicates that the GOI is essential for the surveillance of the fungi, as it would have been lost otherwise. The method presented here allows to test for essentiality of genes when no mutants can be obtained from gene deletion approaches, thereby expanding the toolbox for studying gene function in ascomycetes.

Deletion of codY impairs Staphylococcus epidermidis biofilm formation, generation of viable but non-culturable cells and stimulates cytokine production in human macrophages.

Introduction. Staphylococcus epidermidis biofilms are one of the major causes of bloodstream infections related to the use of medical devices. The diagnosis of these infections is challenging, delaying their treatment and resulting in increased morbidity and mortality rates. As such, it is urgent to characterize the mechanisms employed by this bacterium to endure antibiotic treatments and the response of the host immune system, to develop more effective therapeutic strategies. In several bacterial species, the gene codY was shown to encode a protein that regulates the expression of genes involved in biofilm formation and immune evasion. Additionally, in a previous study, our group generated evidence indicating that codY is involved in the emergence of viable but non-culturable (VBNC) cells in S. epidermidis.Gap statement/Hypothesis. As such, we hypothesized that the gene codY has have an important role in this bacterium virulence.Aim. This study aimed to assess, for the first time, the impact of the deletion of the gene codY in S. epidermidis virulence, namely, in antibiotic susceptibility, biofilm formation, VBNC state emergence and in vitro host immune system response.Methodology. Using an allelic replacement strategy, we constructed and then characterized an S. epidermidis strain lacking codY, in regards to biofilm and VBNC cell formation, susceptibility to antibiotics as well as their role in the interaction with human blood and plasma. Additionally, we investigate whether the codY gene can impact the activation of innate immune cells by evaluating the production of both pro- and anti-inflammatory cytokines by THP-1 macrophages.Results. We demonstrated that the deletion of the gene codY resulted in biofilms with less c.f.u. counts and fewer VBNC cells. Furthermore, we show that although WT and mutant cells were similarly internalized in vitro by human macrophages, a stronger cytokine response was elicited by the mutant in a toll-like receptor 4-dependent manner.Conclusion. Our results indicate that codY contributes to S. epidermidis virulence, which in turn may have an impact on our ability to manage the biofilm-associated infections caused by this bacterium.

RUFY4 deletion prevents pathological bone loss by blocking endo-lysosomal trafficking of osteoclasts.

Mature osteoclasts degrade bone matrix by exocytosis of active proteases from secretory lysosomes through a ruffled border. However, the molecular mechanisms underlying lysosomal trafficking and secretion in osteoclasts remain largely unknown. Here, we show with GeneChip analysis that RUN and FYVE domain-containing protein 4 (RUFY4) is strongly upregulated during osteoclastogenesis. Mice lacking Rufy4 exhibited a high trabecular bone mass phenotype with abnormalities in osteoclast function in vivo. Furthermore, deleting Rufy4 did not affect osteoclast differentiation, but inhibited bone-resorbing activity due to disruption in the acidic maturation of secondary lysosomes, their trafficking to the membrane, and their secretion of cathepsin K into the extracellular space. Mechanistically, RUFY4 promotes late endosome-lysosome fusion by acting as an adaptor protein between Rab7 on late endosomes and LAMP2 on primary lysosomes. Consequently, Rufy4-deficient mice were highly protected from lipopolysaccharide- and ovariectomy-induced bone loss. Thus, RUFY4 plays as a new regulator in osteoclast activity by mediating endo-lysosomal trafficking and have a potential to be specific target for therapies against bone-loss diseases such as osteoporosis.

Uncharacterized yeast gene YBR238C, an effector of TORC1 signaling in a mitochondrial feedback loop, accelerates cellular aging via HAP4- and RMD9-dependent mechanisms.

Uncovering the regulators of cellular aging will unravel the complexity of aging biology and identify potential therapeutic interventions to delay the onset and progress of chronic, aging-related diseases. In this work, we systematically compared genesets involved in regulating the lifespan of Saccharomyces cerevisiae (a powerful model organism to study the cellular aging of humans) and those with expression changes under rapamycin treatment. Among the functionally uncharacterized genes in the overlap set, YBR238C stood out as the only one downregulated by rapamycin and with an increased chronological and replicative lifespan upon deletion. We show that YBR238C and its paralog RMD9 oppositely affect mitochondria and aging. YBR238C deletion increases the cellular lifespan by enhancing mitochondrial function. Its overexpression accelerates cellular aging via mitochondrial dysfunction. We find that the phenotypic effect of YBR238C is largely explained by HAP4- and RMD9-dependent mechanisms. Furthermore, we find that genetic- or chemical-based induction of mitochondrial dysfunction increases TORC1 (Target of Rapamycin Complex 1) activity that, subsequently, accelerates cellular aging. Notably, TORC1 inhibition by rapamycin (or deletion of YBR238C) improves the shortened lifespan under these mitochondrial dysfunction conditions in yeast and human cells. The growth of mutant cells (a proxy of TORC1 activity) with enhanced mitochondrial function is sensitive to rapamycin whereas the growth of defective mitochondrial mutants is largely resistant to rapamycin compared to wild type. Our findings demonstrate a feedback loop between TORC1 and mitochondria (the TORC1-MItochondria-TORC1 (TOMITO) signaling process) that regulates cellular aging processes. Hereby, YBR238C is an effector of TORC1 modulating mitochondrial function.

Simultaneous deletion of ORMDL1 and ORMDL3 proteins disrupts immune cell homeostasis.

ORMDL3 is a prominent member of a family of highly conserved endoplasmic reticulum resident proteins, ORMs (ORM1 and ORM2) in yeast, dORMDL in Drosophila and ORMDLs (ORMDL1, ORMDL2, and ORMDL3) in mammals. ORMDL3 mediates feedback inhibition of de novo sphingolipid synthesis. Expression levels of ORMDL3 are associated with the development of inflammatory and autoimmune diseases including asthma, systemic lupus erythematosus, type 1 diabetes mellitus and others. It has been shown that simultaneous deletions of other ORMDL family members could potentiate ORMDL3-induced phenotypes. To understand the complex function of ORMDL proteins in immunity in vivo, we analyzed mice with single or double deletions of Ormdl genes. In contrast to other single and double knockouts, simultaneous deletion of ORMDL1 and ORMDL3 proteins disrupted blood homeostasis and reduced immune cell content in peripheral blood and spleens of mice. The reduced number of splenocytes was not caused by aberrant immune cell homing. A competitive bone marrow transplantation assay showed that the development of Ormdl1-/-/Ormdl3-/- B cells was dependent on lymphocyte intrinsic factors. Highly increased sphingolipid production was observed in the spleens and bone marrow of Ormdl1-/-/Ormdl3-/- mice. Slight, yet significant, increase in some sphingolipid species was also observed in the spleens of Ormdl3-/- mice and in the bone marrow of both, Ormdl1-/- and Ormdl3-/- single knockout mice. Taken together, our results demonstrate that the physiological expression of ORMDL proteins is critical for the proper development and circulation of lymphocytes. We also show cell-type specific roles of individual ORMDL family members in the production of different sphingolipid species.

Nonlethal deleterious mutation-induced stress accelerates bacterial aging.

Random mutagenesis, including when it leads to loss of gene function, is a key mechanism enabling microorganisms' long-term adaptation to new environments. However, loss-of-function mutations are often deleterious, triggering, in turn, cellular stress and complex homeostatic stress responses, called "allostasis," to promote cell survival. Here, we characterize the differential impacts of 65 nonlethal, deleterious single-gene deletions on Escherichia coli growth in three different growth environments. Further assessments of select mutants, namely, those bearing single adenosine triphosphate (ATP) synthase subunit deletions, reveal that mutants display reorganized transcriptome profiles that reflect both the environment and the specific gene deletion. We also find that ATP synthase α-subunit deleted (ΔatpA) cells exhibit elevated metabolic rates while having slower growth compared to wild-type (wt) E. coli cells. At the single-cell level, compared to wt cells, individual ΔatpA cells display near normal proliferation profiles but enter a postreplicative state earlier and exhibit a distinct senescence phenotype. These results highlight the complex interplay between genomic diversity, adaptation, and stress response and uncover an "aging cost" to individual bacterial cells for maintaining population-level resilience to environmental and genetic stress; they also suggest potential bacteriostatic antibiotic targets and -as select human genetic diseases display highly similar phenotypes, - a bacterial origin of some human diseases.

[The value of minimal residual disease and IKZF1 deletion for predicting prognosis in adult patients with B-cell acute lymphoblastic leukemia].

Objective: To reassess the prognostic value of minimal residual disease (MRD) and IKZF1 gene deletions in adults with B-cell acute lymphoblastic leukemia (B-ALL) who received pediatric-specific chemotherapy regimens during the Nanfang Hospital PDT-ALL-2016 trial. Methods: We retrospectively analyzed the prognosis of 149 adult patients with B-ALL who were admitted to Nanfang Hospital from January 2016 to September 2020. Prognostic factors were identified using Cox regression models. Results: The complete remission rate was 93.2% in 149 patients, with a 5-year overall survival (OS) rate of (54.3±5.0) % and a cumulative incidence of relapse (CIR) of (47.5±5.2) %. The Cox regression analysis revealed that MRD positivity at day 45 (MRD(3)) after induction therapy was independently associated with relapse risk (HR=2.535, 95%CI 1.122-5.728, P=0.025). Deletion of IKZF1 gene was independently associated with mortality risk (HR=1.869, 95%CI 1.034-3.379, P=0.039). Based on MRD(3) and IKZF1 gene status, we categorized adult patients with B-ALL into the low-risk (MRD(3)-negative and IKZF1 gene deletion-negative) and high-risk (MRD(3)-positive and/or IKZF1 gene wild type) groups. The 5-year OS and CIR rates were (45.5±6.0) % vs (69.4±8.6) % (P<0.001) and (61.6±8.3) % vs (25.5±6.5) % (P<0.001), respectively, in the high-risk and low-risk groups, respectively. The multivariate analysis showed that the high-risk group was an independent risk factor for OS (HR=3.937, 95%CI 1.975-7.850, P<0.001) and CIR (HR=4.037, 95%CI 2.095-7.778, P<0.001) . Conclusion: The combined use of MRD and IKZF1 gene in prognostic stratification can improve clinical outcome prediction in adult patients with B-ALL, helping to guide their treatment.

Conditional deletion of neurexin-2 impaired behavioral flexibility to alterations in action-outcome contingency.

Neurexins (Nrxns) are critical for synapse organization and their mutations have been documented in autism spectrum disorder, schizophrenia, and epilepsy. We recently reported that conditional deletion of Nrxn2, under the control of Emx1Cre promoter, predominately expressed in the neocortex and hippocampus (Emx1-Nrxn2 cKO mice) induced stereotyped patterns of behavior in mice, suggesting behavioral inflexibility. In this study, we investigated the effects of Nrxn2 deletion through two different conditional approaches targeting presynaptic cortical neurons projecting to dorsomedial striatum on the flexibility between goal-directed and habitual actions in response to devaluation of action-outcome (A-O) contingencies in an instrumental learning paradigm or upon reversal of A-O contingencies in a water T-maze paradigm. Nrxn2 deletion through both the conditional approaches induced an inability of mice to discriminate between goal-directed and habitual action strategies in their response to devaluation of A-O contingency. Emx1-Nrxn2 cKO mice exhibited reversal learning deficits, indicating their inability to adopt new action strategies. Overall, our studies showed that Nrxn2 deletion through two distinct conditional deletion approaches impaired flexibility in response to alterations in A-O contingencies. These investigations can lay the foundation for identification of novel genetic factors underlying behavioral inflexibility.

[Construction and characterization of a modA gene mutant strain of Klebsiella pneumoniae].

OBJECTIVE: To construct a mutant strain of Klebsiella pneumoniae NTUH- K2044 with modA gene deletion and its complementary strain and explore the role of modA gene in modulating anaerobic nitrate respiratory growth and phenotypes of K. pneumoniae. METHODS: The modA deletion mutant K. pneumoniae strain was constructed by homologous recombination using the suicide vector pKO3-Km. To obtain the complementary strain C-modA, the whole sequence fragment containing the promoter, open reading frame and terminator regions of modA was cloned into pGEM-T-easy and electrically transformed into the modA deletion mutant. The NTUH-K2044 wild-type strain, modA gene deletion mutant and complementary strain were compared by measuring in vitro anaerobic nitrate respiration growth, competitiveness index, biofilm quantification, mucoviscosity assay and morphological measurement using Image J. RESULTS: The modA deletion mutant strain ΔmodA and the complementary strain C-modA were successfully constructed. The modA gene knockout strain showed inhibited anaerobic nitrate respiratory growth compared with the wild- type and C-modA strains with significantly weakened competitiveness, reduced capacity of biofilm synthesis during anaerobiosis, and lowered mucoviscosity under anaerobic conditions. The ΔmodA strain showed a spherical morphology in anaerobic conditions as compared with the normal short rod-like morphology of K. pneumoniae, with also distinctly shorter length than the wild-type and C-modA strains. CONCLUSION: The molybdate transport system encoding gene modA is associated with the pathogenic capacity of K. pneumoniae by modulating its anaerobic nitrate respiration, competitiveness, biofilm formation, hypermucoviscous phenotype and morphology.

Activation of secondary metabolite gene clusters in Chaetomium olivaceum via the deletion of a histone deacetylase.

Histone acetylation modifications in filamentous fungi play a crucial role in epigenetic gene regulation and are closely linked to the transcription of secondary metabolite (SM) biosynthetic gene clusters (BGCs). Histone deacetylases (HDACs) play a pivotal role in determining the extent of histone acetylation modifications and act as triggers for the expression activity of target BGCs. The genus Chaetomium is widely recognized as a rich source of novel and bioactive SMs. Deletion of a class I HDAC gene of Chaetomium olivaceum SD-80A, g7489, induces a substantial pleiotropic effect on the expression of SM BGCs. The C. olivaceum SD-80A ∆g7489 strain exhibited significant changes in morphology, sporulation ability, and secondary metabolic profile, resulting in the emergence of new compound peaks. Notably, three polyketides (A1-A3) and one asterriquinone (A4) were isolated from this mutant strain. Furthermore, our study explored the BGCs of A1-A4, confirming the function of two polyketide synthases (PKSs). Collectively, our findings highlight the promising potential of molecular epigenetic approaches for the elucidation of novel active compounds and their biosynthetic elements in Chaetomium species. This finding holds great significance for the exploration and utilization of Chaetomium resources. KEY POINTS: • Deletion of a class I histone deacetylase activated secondary metabolite gene clusters. • Three polyketides and one asterriquinone were isolated from HDAC deleted strain. • Two different PKSs were reported in C. olivaceum SD-80A.

Podocyte-Specific Deletion of MCP-1 Fails to Protect against Angiotensin II- or Adriamycin-Induced Glomerular Disease.

Investigating the role of podocytes in proteinuric disease is imperative to address the increasing global burden of chronic kidney disease (CKD). Studies strongly implicate increased levels of monocyte chemoattractant protein-1 (MCP-1/CCL2) in proteinuric CKD. Since podocytes express the receptor for MCP-1 (i.e., CCR2), we hypothesized that podocyte-specific MCP-1 production in response to stimuli could activate its receptor in an autocrine manner, leading to further podocyte injury. To test this hypothesis, we generated podocyte-specific MCP-1 knockout mice (Podo-Mcp-1fl/fl) and exposed them to proteinuric injury induced by either angiotensin II (Ang II; 1.5 mg/kg/d, osmotic minipump) or Adriamycin (Adr; 18 mg/kg, intravenous bolus). At baseline, there were no between-group differences in body weight, histology, albuminuria, and podocyte markers. After 28 days, there were no between-group differences in survival, change in body weight, albuminuria, kidney function, glomerular injury, and tubulointerstitial fibrosis. The lack of protection in the knockout mice suggests that podocyte-specific MCP-1 production is not a major contributor to either Ang II- or Adr-induced glomerular disease, implicating that another cell type is the source of pathogenic MCP-1 production in CKD.

[Efficiency of CNV-seq in detecting fetal DMD gene deletion or duplication in prenatal diagnosis].

Objective: To evaluate the diagnostic efficiency of copy number variation sequencing (CNV-seq) to detect the deletion or duplication of DMD gene in prenatal diagnosis. Methods: A retrospective analysis was carried out on the CNV-seq results of 34 544 fetuses diagnosed in the First People's Hospital of Yunnan Province from January 2018 to July 2023. A total of 156 cases of fetuses were collected, including Group 1:125 cases with family history of Duchenne muscular dystrophy or Becker muscular dystrophy (DMD/BMD), and Group 2:31 cases with no family history but a DMD gene deletion or duplication was detected unexpectedly by CNV-seq. Multiplex ligation-dependent probe amplification (MLPA) was used as a standard method to detect the deletion or duplication. Consistency test was carried out basing on the results of CNV-seq and MLPA of all 156 cases. Results: Comparing to MLPA, CNV-seq had a coincidence rate of 92.3% (144/156) for DMD gene deletion or duplication, with a sensitivity and positive predictive value of 88.2%, with a specificity and negative predictive value of 94.3%, a missed detection rate of 3.8%, and a Kappa value of 0.839. CNV-seq missed 4 cases with deletions and 2 with duplications due to involved fragments less than 100 Kb, among 20 cases of deletions and 6 cases of duplications detected by MLPA in Group 1. In Group 2, the deletions and duplications detected by CNV-seq were 42% (13/31) and 58% (18/31), respectively, in which the percentage of duplication was higher than that in Group 1. Among those 18 cases with duplications, 3 cases with duplication locating in exon 42~67 were likely pathogenic; while 9 cases with duplication covering the 5' or 3' end of the DMD gene, containing exon 1 or 79 and with only one breakpoint within the gene, along with the last 6 cases with duplications locating at chrX: 32650635_32910000 detected only by CNV-seq, which might be judged as variants of uncertain significance. Conclusions: CNV-seq has a good efficiency to detect fetal DMD gene deletion or duplication in prenatal diagnosis, while a further verification test by MLPA is recommended. The duplications on chrX: 32650635_32910000, 5' or 3' end of DMD gene detected by CNV-seq should be carefully verified and assessed because those variants appear to be nonpathogenic polymorphisms.

Deletion of yghZ in Escherichia coli promotes growth in presence of furfural with xylose as carbon source.

Thermo-acidic pretreatment of lignocellulosic biomass is required to make it amenable to microbial metabolism and results in generation of furfural due to breakdown of pentose sugars. Furfural is toxic to microbial metabolism and results in reduced microbial productivity and increased production costs. This study asks if deletion of yghZ gene which encodes a NADPH-dependent aldehyde reductase enzyme results in improved furfural tolerance in Escherichia coli host. The ∆yghZ strain-SSK201-was tested for tolerance to furfural in presence of 5% xylose as a carbon source in AM1 minimal medium. At 96 h and in presence of 1.0 g/L furfural, the culture harboring strain SSK201 displayed 4.5-fold higher biomass, 2-fold lower furfural concentration and 15.75-fold higher specific growth rate (µ) as compared to the parent strain SSK42. The furfural tolerance advantage of SSK201 was retained when the carbon source was switched to glucose in AM1 medium and was lost in rich LB medium. The findings have potential to be scaled up to a hydrolysate culture medium, which contains furan inhibitors and lack nutritionally rich components, under bioreactor cultivation and observe growth advantage of the ∆yghZ host. It harbors potential to generate robust industrial strains which can convert lignocellulosic carbon into metabolites of interest in a cost-efficient manner.

Maltose accumulation-induced cell death in Saccharomyces cerevisiae.

Pretreatment of lignocellulose yields a complex sugar mixture that potentially can be converted into bioethanol and other chemicals by engineered yeast. One approach to overcome competition between sugars for uptake and metabolism is the use of a consortium of specialist strains capable of efficient conversion of single sugars. Here, we show that maltose inhibits cell growth of a xylose-fermenting specialist strain IMX730.1 that is unable to utilize glucose because of the deletion of all hexokinase genes. The growth inhibition cannot be attributed to a competition between maltose and xylose for uptake. The inhibition is enhanced in a strain lacking maltase enzymes (dMalX2) and completely eliminated when all maltose transporters are deleted. High-level accumulation of maltose in the dMalX2 strain is accompanied by a hypotonic-like transcriptional response, while cells are rescued from maltose-induced cell death by the inclusion of an extracellular osmolyte such as sorbitol. These data suggest that maltose-induced cell death is due to high levels of maltose uptake causing hypotonic-like stress conditions and can be prevented through engineering of the maltose transporters. Transporter engineering should be included in the development of stable microbial consortia for the efficient conversion of lignocellulosic feedstocks.

[Methylthioadenosine phosphorylase and p16 as surrogate diagnostic markers for CDKN2A homozygous deletion in brain tumors].

Objective: To examine whether immunohistochemistry of methylthioadenosine phosphorylase (MTAP) and p16 could be used to predict the CDKN2A status in various brain tumors. Methods: A total of 118 cases of IDH-mutant astrocytomas, 16 IDH-wildtype glioblastoma, 17 polymorphic xanthoastrocytoma (PXA) and 20 meningiomas diagnosed at Xuanwu Hospital, Capital Medical University, Beijing, China from November 2017 to October 2023 were collected and analyzed. The CDKN2A status was detected by using fluorescence in situ hybridization or next-generation sequencing. Expression of MTAP and p16 proteins was detected with immunohistochemistry. The association of loss of MTAP/p16 expression with CDKN2A homozygous/heterozygous deletion was examined. Results: Among the 118 cases of IDH-mutant astrocytoma, 13 cases showed homozygous deletion of CDKN2A. All of them had no expression of MTAP while 9 cases had no expression of p16. Among the 16 cases of IDH wild-type glioblastoma, 6 cases showed homozygous deletion of CDKN2A. All 6 cases had no expression of MTAP, while 3 of these cases had no expression of p16 expression. Among the 17 PXA cases, 4 cases showed homozygous deletion of CDKN2A, and the expression of MTAP and p16 was also absent in these 4 cases. Among the 20 cases of meningiomas, 4 cases showed homozygous deletion of CDKN2A. Their expression of MTAP and p16 was also absent. Among the four types of brain tumors, MTAP was significantly correlated with CDKN2A homozygous deletion (P<0.05), with a sensitivity of 100%. However, it was only significantly correlated with the loss of heterozygosity (LOH) of CDKN2A in astrocytomas (P<0.001). P16 was associated with CDKN2A homozygous deletion in IDH-mutant astrocytoma and PXA (P<0.001), but not with the LOH of CDKN2A. Its sensitivity and specificity were lower than that of MTAP. Conclusions: MTAP could serve as a predictive surrogate for CDKN2A homozygous deletion in adult IDH-mutant astrocytoma, PXA, adult IDH-wildtype glioblastoma and meningioma. However, p16 could only be used in the first two tumor types, and its specificity and sensitivity are lower than that of MTAP.