Lateral sacral artery aneurysm.

A rare case of aneurysm of the lateral sacral artery is reported. This 46-year-old female presented with complaints of bowel and bladder incontinence and decreased perianal sensation for the past 15 months. She underwent laminectomy and diskectomy for the diagnosis of a prolapsed disk at peripheral hospital where the surgeon was confronted with a severe and unexpected hemorrhage, and surgery was aborted without effective treatment. Prior medical history includes hypertensive kidney disease with a renal transplant eight years ago. Magnetic resonance imaging and angiographic findings were suggestive of a lateral sacral artery aneurysm. Patient with a history of renal transplant and presenting with cauda equina require a more thorough assessment, and a differential of lateral sacral artery aneurysm should always be kept in mind. Our purpose is to report the pre-operative features of the lateral sacral artery aneurysm and its treatment modalities.

Functional outcomes in intradural extramedullary spinal tumors.

Background: Intradural extramedullary (IDEM) spinal cord tumors account for approximately two-thirds of benign intraspinal neoplasms. These are amenable to gross total excision but can have variable functional outcomes, which plays a key role in assessing their impact on a patient's quality of life. Understanding the functional outcomes associated with these tumors is crucial for healthcare professionals to devise appropriate treatment plans and provide comprehensive care. Methods: In this study, we retrospectively reviewed the outcomes of 130 patients with IDEM tumors who underwent surgery in the past six years between January 2017 and December 2022 at a single institution. Patient demographics, symptoms, and tumor characteristics (anatomical and pathological) in all operated spinal IDEM tumors were analyzed. The neurological findings obtained during the preoperative stage and the postoperative follow-up were evaluated according to the Frankel grading. The back pain was assessed using the Denis pain scale (DPS). Results: The age range, gender distribution, presentation, histopathology, and tumor characteristics were analyzed. The histopathological outcomes of the study were as follows: 56 cases of schwannoma, 37 cases of meningiomas, 16 patients of neurofibroma, six cases of epidermoid cyst, five cases each of ependymoma and dermoid cyst, three cases of arachnoid cyst, two cases of metastasis, and one case of paraganglioma. Pain was the most common symptom (38.5%), followed by weakness in limbs (31.5%), paresthesia/numbness (22.3%), and sphincter disturbance (7.7%). Complete total resection was seen in 93% of cases, with 7% undergoing subtotal excision. The complications encountered were - four cases of surgical site infection and one case each of cerebrospinal fluid leak, pseudomeningocele, and epidural hematoma. In our series, 49.3% of patients had significantly good improvement in functional outcomes as per improvement in Frankel score, and 43% of patients had good functional improvement. Significant functional improvement was noted at immediate postoperative follow-up, 2-week follow-up, and six-month follow-up periods. Reoccurrence was seen in 7 cases (5.4%). The DPS score mean values showed a significant decrease over the follow-up duration as compared to preoperative mean values. Significantly poor outcome was seen in IDEM tumours present anteriorly. Conclusion: The IDEM tumors are usually benign and are readily detected by contrast-enhanced magnetic resonance imaging scans. These have variable functional outcomes in different centers. Assessing this functional outcome is an essential aspect of managing IDEM spinal tumors. It was observed through our study that the ventral location of the tumor, thoracic tumors, and poor preoperative neurological status of the patient correspond with poorer postoperative functional outcomes. Furthermore, a significant decrease in the pain symptoms with improvement of Frankel score was seen postoperatively, thus this being suggestive of a significant improvement of functional outcome after surgery. This study helps to conclude that the morbidity associated with the resection of IDEM tumors is not as significant as originally thought to be.

Clinical Outcome for Lumbar Disc Herniation Treatment with Intradiscal Oxygen-ozone Therapy.

BACKGROUND: Low back pain due to disc herniation is a common problem causing frequent hospital visits and loss of working days with major socio-economic impact. Conservative treatments like analgesics, physiotherapy do not work in all patients. Surgical treatment has been the mainstay of treatment when indicated but is associated with anesthetic and surgical complications. Intradiscal oxygen-ozone chemonucleolysis is a minimally invasive procedure done under local anesthesia and has promising role in shrinking the bulged disc and reducing nerve root compression and related symptoms. This retrospective study was done to see how intradiscal oxygen-ozone chemonucleolysis reduces pain severity in patients with discogenic low back pain. METHODS: Retrospective data were retrieved of those patients who underwent fluoroscopy guided intradiscal oxygen-ozone chemonucleolysis with 5-6 ml of an O2-O3 mixture (concentration of 30 microgram/ml) during a period of two years in Nepal pain care and research center. Numerical pain scale (NRS) at various follow ups were compared to preprocedural NRS. RESULTS: Preprocedural NRS was 8± 13. NRS at three hours, one week, one month, three months and six months were 2± 13 (73 percent reduction), 2± 53 (68 percent reduction), 2± 27 (72 percent reduction), 1± 08 (77 percent reduction) and 1± 67 (79 percent reduction) respectively. CONCLUSIONS: Intradiscal oxygen-ozone chemonucleolysis can be a useful modality of treatment for discogenic low back pain in patients who fail to respond to conservative management and in whom surgery is not indicated.

Integration of urban ecosystem-based adaptation in Nepal: A policy landscape analysis.

Ecosystem-based adaptation (EbA) is an ecologically sensitive, cost-effective, and locally adaptive climate adaptation strategy to strengthen the climate resilience of vulnerable communities. While many studies on EbA have been conducted in rural and mountainous regions or within the natural sciences realm, there is a lack of comprehensive research that assesses how urban EbA measures have been incorporated into existing policies and plans in Global South, including in Nepal. Ecosystem-based adaptation is in the early stages of its establishment as a fundamental component to address climate adaptation and sustainable development in urban environments. Accordingly, effective integration strategies, challenges, potential focal areas, and entry points have yet to be extensively studied. To address the literature gap, this paper analyses the types of EbA interventions and the extent of urban EbA integration within Nepal's climate, urban, and sectoral policies and plans. Direct content analysis and a qualitative scoring system were used to evaluate the plan components and assess the level of EbA integration. The findings indicate that the policies and plans recognise the importance of conserving, enhancing, and managing ecosystems for climate change adaptation, and EbA measures are mainly included in action-oriented sections. However, the results also reveal inadequate EbA integration, particularly in the information base, vision and objectives, and implementation aspects. The implementation component notably lacks comprehensive provisions for budget allocation, responsible authorities, definite timelines, and clear roadmaps. The breakdown of EbA integration in the policies and plans suggests that climate and urban plans substantially integrate urban EbA measures, but discrepancies exist with climate and urban policies and sectoral policies and plans. These findings collectively emphasise a pressing need to enhance the recognition and integration of urban EbA measures within policy frameworks with a view towards strengthening climate resilience and mitigating climate-related hazards in urban environments.

Regulation of mTORC1 by the Rag GTPases.

The Rag GTPases are an evolutionarily conserved family that play a crucial role in amino acid sensing by the mammalian target of rapamycin complex 1 (mTORC1). mTORC1 is often referred to as the master regulator of cell growth. mTORC1 hyperactivation is observed in multiple diseases such as cancer, obesity, metabolic disorders, and neurodegeneration. The Rag GTPases sense amino acid levels and form heterodimers, where RagA or RagB binds to RagC or RagD, to recruit mTORC1 to the lysosome where it becomes activated. Here, we review amino acid signaling to mTORC1 through the Rag GTPases.

Use of the Western blot technique to identify the immunogenic proteins of Borrelia burgdorferi for developing a Lyme disease vaccine.

BACKGROUND: Lyme disease is a serious infectious disease having a restricted worldwide distribution for which there is no vaccine available for human use. OBJECTIVE: This study was designed to determine common reactive antigens involved in Borrelia burgdorferi (Bb) infection that are recognized in mammalian sera that may be useful for vaccine development. METHODS: Blood samples were collected from patients with documented Lyme disease, and from rabbits and mice experimentally infected with either tick-transmitted or culture-grown Borrelia burgdorferi. All samples were then processed for sera. For performing the Western blots, sonicated Bb organisms (whole cell lysates) and protein ladders were separated by protein gel electrophoresis. Immune reactivities of the electrophoresed proteins with the serum samples were then probed with anti-HRP IgG reagent. RESULTS: Rabbit, mouse and human sera consistently reacted with the 41 kDa band of Bb which corresponded to the flagellin protein - the major protein component of this organism's periplasmic flagella, also known as axial filaments or fibrils. Various other Bb antigens of wide molecular weight ranges were also recognized by rabbit and human sera, and less frequently with mouse sera. CONCLUSION: The strong immune response to the 41 kDa flagellin protein by the different mammalian species suggests the utility of a possible vaccine targeting this protein, although other proteins may also be appropriate, for preventing Lyme disease following a bite from an infected tick.

Looking into the Laboratory Staffing Issues that Affected Ambulatory Care Clinical Laboratory Operations during the COVID-19 Pandemic.

OBJECTIVE: Our New York City Municipal Public Health System-based multisite ambulatory and school-based Gotham Health clinics offer waived point-of-care tests and provider-performed microscopy to the local communities. Our Gotham Health laboratory service conducts system-wide centralized implementation, monitoring, and oversight of the POCT operations. Laboratory staffing has always been an issue for us as there is a decades-long shortage of laboratory staff, primarily licensed medical technologists and technicians, in New York, like many other states. Our clinical laboratory operations team struggled to hire qualified people even before the COVID-19 pandemic onset. It has faced more significant challenges with the emergence of SARS-CoV-2 pandemic cases in New York City and across the country since mid-March 2020. METHODS: As staffing continues to be a struggle, it directly affected the POCT performances and a system-wide reduction in the test numbers during the pandemic. We investigated to identify the factors that made staffing more challenging. RESULTS: The impact on our POCT started after laboratory staff relocated to the acute care hospital laboratories to provide testing support during the pandemic's peak. That caused significant delays or complete cessation of POCT operations in the clinics due to a lack of oversight support. We also experienced the risk of more vacated positions where staff already feel overworked, overwhelmed, and emotionally drained, causing professional burnout. The significant challenges identified are noncompliance with vaccine mandates resulting in job dismissal and voluntary resignations in exchange for higher-paying laboratories. Finally, the other challenges identified were frequent sick calls due to mental fatigue, retirement of seasoned staff, and inability to attract qualified technologists to meet the demands of increasing test-ordering patterns. CONCLUSIONS: Determining the factors that culminated in the staffing issues becoming more challenging during the COVID-19 pandemic in our ambulatory care clinic laboratory operations will help us in future crisis planning and mitigation.

Upper Gastrointestinal Bleeding among Patients Admitted in Department of Emergency in a Tertiary Care Centre: A Descriptive Cross-sectional Study.

Introduction: Upper gastrointestinal bleeding is a common medical emergency with significant morbidity and mortality. Its causes can be classified under variceal bleeding or non-variceal bleeding. Peptic ulcer and variceal bleeding are common causes. Thus, this study aims to find the prevalence of upper gastrointestinal bleeding among patients attending the Department of Emergency in a tertiary care centre. Methods: This was a descriptive cross-sectional study conducted on patients admitted to the Department of Emergency a tertiary care centre from September 2020 to August 2021 among 3375 patients. The ethical approval was obtained from the Institutional Review Committee of the hospital (Reference number: 328). Patients presenting with the clinical features of upper gastrointestinal bleeding in the form of hematemesis or melena were enrolled after written informed consent. Data entry was done in Statistical Packages for the Social Sciences version 20.0. for descriptive analysis. Point estimate at 95% Confidence Interval was calculated along with frequency and percentage for binary data. Results: Out of 3375 admissions in the Department of Emergency, 85 (2.52%) (1.99-3.05 at 95% Confidence Interval) patients presented with upper gastrointestinal bleeding. Conclusions: The prevalence of upper gastrointestinal bleeding is lower in comparison to other studies done in similar settings. Keywords: bleeding; emergency medicine; upper gastrointestinal tract; varices.

SNAT7 regulates mTORC1 via macropinocytosis.

Mammalian target of rapamycin complex 1 (mTORC1) senses amino acids to control cell growth, metabolism, and autophagy. Some amino acids signal to mTORC1 through the Rag GTPase, whereas glutamine and asparagine activate mTORC1 through a Rag GTPase-independent pathway. Here, we show that the lysosomal glutamine and asparagine transporter SNAT7 activates mTORC1 after extracellular protein, such as albumin, is macropinocytosed. The N terminus of SNAT7 forms nutrient-sensitive interaction with mTORC1 and regulates mTORC1 activation independently of the Rag GTPases. Depletion of SNAT7 inhibits albumin-induced mTORC1 lysosomal localization and subsequent activation. Moreover, SNAT7 is essential to sustain KRAS-driven pancreatic cancer cell growth through mTORC1. Thus, SNAT7 links glutamine and asparagine signaling from extracellular protein to mTORC1 independently of the Rag GTPases and is required for macropinocytosis-mediated mTORC1 activation and pancreatic cancer cell growth.

G-Protein Coupled Receptor Signaling and Mammalian Target of Rapamycin Complex 1 Regulation.

The mammalian target of rapamycin (mTOR) senses upstream stimuli to regulate numerous cellular functions such as metabolism, growth, and autophagy. Increased activation of mTOR complex 1 (mTORC1) is typically observed in human disease and continues to be an important therapeutic target. Understanding the upstream regulators of mTORC1 will provide a crucial link in targeting hyperactivated mTORC1 in human disease. In this mini-review, we will discuss the regulation of mTORC1 by upstream stimuli, with a specific focus on G-protein coupled receptor signaling to mTORC1. SIGNIFICANCE STATEMENT: mTORC1 is a master regulator of many cellular processes and is often hyperactivated in human disease. Therefore, understanding the molecular underpinnings of G-protein coupled receptor signaling to mTORC1 will undoubtedly be beneficial for human disease.

Quantitative Longitudinal Imaging Reveals that Inhibiting Hedgehog Activity Alleviates the Hypoxic Tumor Landscape.

Metastases account for the majority of mortalities related to breast cancer. The onset and sustained presence of hypoxia strongly correlates with increased incidence of metastasis and unfavorable prognosis in patients with breast cancer. The Hedgehog (Hh) signaling pathway is dysregulated in breast cancer, and its abnormal activity enables tumor progression and metastasis. In addition to programming tumor cell behavior, Hh activity enables tumor cells to craft a metastasis-conducive microenvironment. Hypoxia is a prominent feature of growing tumors that impacts multiple signaling circuits that converge upon malignant progression. We investigated the role of Hh activity in crafting a hypoxic environment of breast cancer. We used radioactive tracer [18F]-fluoromisonidazole (FMISO) positron emission tomography (PET) to image tumor hypoxia. We show that tumors competent for Hh activity are able to establish a hypoxic milieu; pharmacologic inhibition of Hh signaling in a syngeneic mammary tumor model mitigates tumor hypoxia. Furthermore, in hypoxia, Hh activity is robustly activated in tumor cells and institutes increased HIF signaling in a VHL-dependent manner. The findings establish a novel perspective on Hh activity in crafting a hypoxic tumor landscape and molecularly navigating the tumor cells to adapt to hypoxic conditions. IMPLICATIONS: Importantly, we present a translational strategy of utilizing longitudinal hypoxia imaging to measure the efficacy of vismodegib in a preclinical model of triple-negative breast cancer.

AKAP13 couples GPCR signaling to mTORC1 inhibition.

The mammalian target of rapamycin complex 1 (mTORC1) senses multiple stimuli to regulate anabolic and catabolic processes. mTORC1 is typically hyperactivated in multiple human diseases such as cancer and type 2 diabetes. Extensive research has focused on signaling pathways that can activate mTORC1 such as growth factors and amino acids. However, less is known about signaling cues that can directly inhibit mTORC1 activity. Here, we identify A-kinase anchoring protein 13 (AKAP13) as an mTORC1 binding protein, and a crucial regulator of mTORC1 inhibition by G-protein coupled receptor (GPCR) signaling. GPCRs paired to Gαs proteins increase cyclic adenosine 3'5' monophosphate (cAMP) to activate protein kinase A (PKA). Mechanistically, AKAP13 acts as a scaffold for PKA and mTORC1, where PKA inhibits mTORC1 through the phosphorylation of Raptor on Ser 791. Importantly, AKAP13 mediates mTORC1-induced cell proliferation, cell size, and colony formation. AKAP13 expression correlates with mTORC1 activation and overall lung adenocarcinoma patient survival, as well as lung cancer tumor growth in vivo. Our study identifies AKAP13 as an important player in mTORC1 inhibition by GPCRs, and targeting this pathway may be beneficial for human diseases with hyperactivated mTORC1.

Hedgehog Signaling Regulates Metabolism and Polarization of Mammary Tumor-Associated Macrophages.

Elevated infiltration of immunosuppressive alternatively polarized (M2) macrophages is associated with poor prognosis in patients with cancer. The tumor microenvironment remarkably orchestrates molecular mechanisms that program these macrophages. Here we identify a novel role for oncogenic Hedgehog (Hh) signaling in programming signature metabolic circuitries that regulate alternative polarization of tumor-associated macrophages. Two immunocompetent orthotopic mouse models of mammary tumors were used to test the effect of inhibiting Hh signaling on tumor-associated macrophages. Treatment with the pharmacologic Hh inhibitor vismodegib induced a significant shift in the profile of tumor-infiltrating macrophages. Mass spectrometry-based metabolomic analysis showed Hh inhibition induced significant alterations in metabolic processes, including metabolic sensing, mitochondrial adaptations, and lipid metabolism. In particular, inhibition of Hh in M2 macrophages reduced flux through the UDP-GlcNAc biosynthesis pathway. Consequently, O-GlcNAc-modification of STAT6 decreased, mitigating the immune-suppressive program of M2 macrophages, and the metabolically demanding M2 macrophages shifted their metabolism and bioenergetics from fatty acid oxidation to glycolysis. M2 macrophages enriched from vismodegib-treated mammary tumors showed characteristically decreased O-GlcNAcylation and altered mitochondrial dynamics. These Hh-inhibited macrophages are reminiscent of inflammatory (M1) macrophages, phenotypically characterized by fragmented mitochondria. This is the first report highlighting the relevance of Hh signaling in controlling a complex metabolic network in immune cells. These data describe a novel immunometabolic function of Hh signaling that can be clinically exploited. SIGNIFICANCE: These findings illustrate that Hh activity regulates a metabolic and bioenergetic regulatory program in tumor-associated macrophages that promotes their immune-suppressive polarization.

Normalizing glucose levels reconfigures the mammary tumor immune and metabolic microenvironment and decreases metastatic seeding.

Obesity and diabetes cumulatively create a distinct systemic metabolic pathophysiological syndrome that predisposes patients to several diseases including breast cancer. Moreover, diabetic and obese women with breast cancer show a significant increase in mortality compared to non-obese and/or non-diabetic women. We hypothesized that these metabolic conditions incite an aggressive tumor phenotype by way of impacting tumor cell-autonomous and tumor cell non-autonomous events. In this study, we established a type 2 diabetic mouse model of triple-negative mammary carcinoma and investigated the effect of a glucose lowering therapy, metformin, on the overall tumor characteristics and immune/metabolic microenvironment. Diabetic mice exhibited larger mammary tumors that had increased adiposity with high levels of O-GlcNAc protein post-translational modification. These tumors also presented with a distinct stromal profile characterized by altered collagen architecture, increased infiltration by tumor-permissive M2 macrophages, and early metastatic seeding compared to non-diabetic/lean mice. Metformin treatment of the diabetic/obese mice effectively normalized glucose levels, reconfigured the mammary tumor milieu, and decreased metastatic seeding. Our results highlight the impact of two metabolic complications of obesity and diabetes on tumor cell attributes and showcase metformin's ability to revert tumor cell and stromal changes induced by an obese and diabetic host environment.

Hedgehog signaling enables repair of ribosomal DNA double-strand breaks.

Ribosomal DNA (rDNA) consists of highly repeated sequences that are prone to incurring damage. Delays or failure of rDNA double-strand break (DSB) repair are deleterious, and can lead to rDNA transcriptional arrest, chromosomal translocations, genomic losses, and cell death. Here, we show that the zinc-finger transcription factor GLI1, a terminal effector of the Hedgehog (Hh) pathway, is required for the repair of rDNA DSBs. We found that GLI1 is activated in triple-negative breast cancer cells in response to ionizing radiation (IR) and localizes to rDNA sequences in response to both global DSBs generated by IR and site-specific DSBs in rDNA. Inhibiting GLI1 interferes with rDNA DSB repair and impacts RNA polymerase I activity and cell viability. Our findings tie Hh signaling to rDNA repair and this heretofore unknown function may be critically important in proliferating cancer cells.

An Emerging Regulatory Role for the Tumor Microenvironment in the DNA Damage Response to Double-Strand Breaks.

Radiation, alkylating agents, and platinum-based chemotherapy treatments eliminate cancer cells through the induction of excessive DNA damage. The resultant DNA damage challenges the cancer cell's DNA repair capacity. Among the different types of DNA damage induced in cells, double-strand breaks (DSB) are the most lethal if left unrepaired. Unrepaired DSBs in tumor cells exacerbate existing gene deletions, chromosome losses and rearrangements, and aberrant features that characteristically enable tumor progression, metastasis, and drug resistance. Tumor microenvironmental factors like hypoxia, inflammation, cellular metabolism, and the immune system profoundly influence DSB repair mechanisms. Here, we put into context the role of the microenvironment in governing DSB repair mechanisms.

Intracranial metastasis in fibrolamellar hepatocellular carcinoma.

Fibrolamellar hepatocellular carcinoma (FLHCC) is a rare liver malignancy in adolescents and young adults. Surgery is the mainstay of therapy for primary and metastatic disease. Most patients relapse, with development of both local and distant metastases. Brain metastases from solid tumors are rare in the pediatric and young adult population. Here, we document three patients with brain metastases from FLHCC, confirmed by histology and molecular characterization of the chimeric fusion DNAJB1-PRKACA, each necessitating neurosurgical intervention. These observations highlight the ability of FLHCC to metastasize to the brain and suggest the need for surveillance neuroimaging for patients with advanced-stage disease.

Adipocyte-Lineage Cells Support Growth and Dissemination of Multiple Myeloma in Bone.

Multiple myeloma (MM) cells reside in the bone marrow microenvironment and form complicated interactions with nonneoplastic, resident stromal cells. We previously found that aggressive MM cells shift osteoblast progenitors toward adipogenesis. In addition, adipocytes are among the most common cell types in the adult skeleton; both mature adipocytes and preadipocytes serve as endocrine cells that secrete a number of soluble molecules into the microenvironment. Therefore, we used a combination of in vivo and in vitro methods to test the hypothesis that an increase in adipocyte lineage cells feeds back to promote MM progression. The results of this study revealed that bone marrow from patients with MM indeed contains increased preadipocytes and significantly larger mature adipocytes than normal bone marrow. We also found that preadipocytes and mature adipocytes secrete many molecules important for supporting MM cells in the bone marrow and directly recruit MM cells through both monocyte chemotactic protein-1 and stromal cell-derived factor-1α. Co-culture experiments found that preadipocytes activate Wnt signaling and decrease cleaved caspase-3, whereas mature adipocytes activate ERK signaling in MM cells. Furthermore, mature adipocyte conditioned medium promotes MM growth, whereas co-culture with preadipocytes results in enhanced MM cell chemotaxis in vitro and increased tumor growth in bone in vivo. Combined, these data reveal the importance of preadipocytes and mature adipocytes on MM progression and represent a unique target in the bone marrow microenvironment.

Molecular genetic diversity and characterization of conjugation genes in the fish parasite Ichthyophthirius multifiliis.

Ichthyophthirius multifiliis is the etiologic agent of "white spot", a commercially important disease of freshwater fish. As a parasitic ciliate, I. multifiliis infects numerous host species across a broad geographic range. Although Ichthyophthirius outbreaks are difficult to control, recent sequencing of the I. multifiliis genome has revealed a number of potential metabolic pathways for therapeutic intervention, along with likely vaccine targets for disease prevention. Nonetheless, major gaps exist in our understanding of both the life cycle and population structure of I. multifiliis in the wild. For example, conjugation has never been described in this species, and it is unclear whether I. multifiliis undergoes sexual reproduction, despite the presence of a germline micronucleus. In addition, no good methods exist to distinguish strains, leaving phylogenetic relationships between geographic isolates completely unresolved. Here, we compared nucleotide sequences of SSUrDNA, mitochondrial NADH dehydrogenase subunit I and cox-1 genes, and 14 somatic SNP sites from nine I. multifiliis isolates obtained from four different states in the US since 1995. The mitochondrial sequences effectively distinguished the isolates from one another and divided them into at least two genetically distinct groups. Furthermore, none of the nine isolates shared the same composition of the 14 somatic SNP sites, suggesting that I. multifiliis undergoes sexual reproduction at some point in its life cycle. Finally, compared to the well-studied free-living ciliates Tetrahymena thermophila and Paramecium tetraurelia, I. multifiliis has lost 38% and 29%, respectively, of 16 experimentally confirmed conjugation-related genes, indicating that mechanistic differences in sexual reproduction are likely to exist between I. multifiliis and other ciliate species.

Alternative splicing governs cone cyclic nucleotide-gated (CNG) channel sensitivity to regulation by phosphoinositides.

Precursor mRNA encoding CNGA3 subunits of cone photoreceptor cyclic nucleotide-gated (CNG) channels undergoes alternative splicing, generating isoforms differing in the N-terminal cytoplasmic region of the protein. In humans, four variants arise from alternative splicing, but the functional significance of these changes has been a persistent mystery. Heterologous expression of the four possible CNGA3 isoforms alone or with CNGB3 subunits did not reveal significant differences in basic channel properties. However, inclusion of optional exon 3, with or without optional exon 5, produced heteromeric CNGA3 + CNGB3 channels exhibiting an ∼2-fold greater shift in K1/2,cGMP after phosphatidylinositol 4,5-biphosphate or phosphatidylinositol 3,4,5-trisphosphate application compared with channels lacking the sequence encoded by exon 3. We have previously identified two structural features within CNGA3 that support phosphoinositides (PIPn) regulation of cone CNG channels: N- and C-terminal regulatory modules. Specific mutations within these regions eliminated PIPn sensitivity of CNGA3 + CNGB3 channels. The exon 3 variant enhanced the component of PIPn regulation that depends on the C-terminal region rather than the nearby N-terminal region, consistent with an allosteric effect on PIPn sensitivity because of altered N-C coupling. Alternative splicing of CNGA3 occurs in multiple species, although the exact variants are not conserved across CNGA3 orthologs. Optional exon 3 appears to be unique to humans, even compared with other primates. In parallel, we found that a specific splice variant of canine CNGA3 removes a region of the protein that is necessary for high sensitivity to PIPn. CNGA3 alternative splicing may have evolved, in part, to tune the interactions between cone CNG channels and membrane-bound phosphoinositides.