Assessment of pre-extubating recurrent laryngeal nerve palsy using ultrasound in postoperative patients with esophageal cancer: a prospective observational study.

PURPOSE: Ultrasound performed after extubation has been suggested to be useful for the diagnosis of recurrent laryngeal nerve (RLN) paralysis. However, the use of ultrasound for this purpose before extubation has not been examined. The aim of this study was to examine the versatility (interrater reliability) and usefulness of ultrasound for evaluating the movement of vocal cords before extubation. METHODS: The subjects were 30 patients who underwent radical surgery for esophageal cancer from August 2020 to December 2021. An experienced examiner performed an ultrasound examination before and after elective extubation on the day after surgery to evaluate RLN paralysis and record videos. Bronchoscopy was then performed to make a definite diagnosis. Three anesthetists blinded to the diagnosis also evaluated the cases using the videos, and the versatility of the examination was determined using a kappa test. RESULTS: The diagnostic accuracies of the examiner and three anesthetists were 76.7%, 50.0%, 53.3%, and 46.7%, respectively, and the kappa coefficients for the examiner with the anesthetists were 0.310, 0.502, and 0.169, respectively. The sensitivity, specificity, positive predictive value and negative predictive value for diagnosis of RLN paralysis by the examiner using ultrasound before extubation were 0.57, 0.95, 0.80, and 0.87, respectively. CONCLUSION: These results indicate a lack of versatility of the ultrasound examination based on the low kappa coefficients. However, with an experienced examiner, ultrasound can serve as a non-invasive examination that can be performed before extubation with high accuracy and specificity for diagnosis of postoperative RLN paralysis.

A multicenter, phase 2 study to evaluate the efficacy and safety of osilodrostat, a new 11ß-hydroxylase inhibitor, in Japanese patients with endogenous Cushing's syndrome other than Cushing's disease.

This phase 2, single-arm, open-label, dose-titration, multicenter study evaluated osilodrostat (11ß-hydroxylase inhibitor) in Japanese patients with endogenous Cushing's syndrome (CS) caused by adrenal tumor/hyperplasia or ectopic adrenocorticotropic hormone syndrome. The primary endpoint was percent change from baseline to week 12 in mean urinary free cortisol (mUFC) at the individual patient level. Of the nine patients enrolled in the study, seven completed the 12-week core treatment period and two discontinued at or prior to week 12 due to adverse events (AEs). Of the seven patients who completed 12 weeks of study treatment, two completed 48 weeks of study treatment. Median osilodrostat exposure was 12 weeks. Median (range) average dose including dose interruption (0 mg/day) was 2.143 (1.16-7.54) mg/day. Median (range, population) percentage change in mUFC was -94.47% (-99.0% to -52.6%, n = 7) at week 12. At week 12, 6/9 patients were complete responders (mUFC ≤ upper limit of normal [ULN]) and 1/9 was a partial responder (mUFC > ULN but decreased by ≥50% from baseline). Most frequent AEs were adrenal insufficiency (n = 7), gamma-glutamyl transferase increase, malaise, and nasopharyngitis (n = 3 each). Serious AEs were seen in four patients. No deaths occurred in this study. In conclusion, osilodrostat treatment led to a reduction in mUFC in all nine patients with endogenous CS other than Cushing's disease (CD), regardless of disease type, with >80% reduction seen in 6/7 patients at week 12. The safety profile was consistent with previous reports in CD patients, and the reported AEs were manageable.

Environmental responsiveness of tubulin glutamylation in sensory cilia is regulated by the p38 MAPK pathway.

Glutamylation is a post-translational modification found on tubulin that can alter the interaction between microtubules (MTs) and associated proteins. The molecular mechanisms regulating tubulin glutamylation in response to the environment are not well understood. Here, we show that in the sensory cilia of Caenorhabditis elegans, tubulin glutamylation is upregulated in response to various signals such as temperature, osmolality, and dietary conditions. Similarly, tubulin glutamylation is modified in mammalian photoreceptor cells following light adaptation. A tubulin glutamate ligase gene ttll-4, which is essential for tubulin glutamylation of axonemal MTs in sensory cilia, is activated by p38 MAPK. Amino acid substitution of TTLL-4 has revealed that a Thr residue (a putative MAPK-phosphorylation site) is required for enhancement of tubulin glutamylation. Intraflagellar transport (IFT), a bidirectional trafficking system specifically observed along axonemal MTs, is required for the formation, maintenance, and function of sensory cilia. Measurement of the velocity of IFT particles revealed that starvation accelerates IFT, which was also dependent on the Thr residue of TTLL-4. Similarly, starvation-induced attenuation of avoidance behaviour from high osmolality conditions was also dependent on ttll-4. Our data suggest that a novel evolutionarily conserved regulatory system exists for tubulin glutamylation in sensory cilia in response to the environment.

Efficacy and safety of long-acting pasireotide in Japanese patients with acromegaly or pituitary gigantism: results from a multicenter, open-label, randomized, phase 2 study.

A multicenter, open-label, phase 2 study was conducted to investigate the efficacy and safety of long-acting pasireotide formulation in Japanese patients with acromegaly or pituitary gigantism. Medically naïve or inadequately controlled patients (on somatostatin analogues or dopamine agonists) were included. Primary end point was the proportion of all patients who achieved biochemical control (mean growth hormone [GH] levels<2.5µg/L and normalized insulin-like growth factor-1 [IGF-1]) at month 3. Thirty-three patients (acromegaly, n=32; pituitary gigantism, n=1) were enrolled and randomized 1:1:1 to receive open-label pasireotide 20mg, 40mg, or 60mg. The median age was 52 years (range, 31-79) and 20 patients were males. At month 3, 18.2% of patients (6/33; 90% confidence interval: 8.2%, 32.8%) had biochemical control (21.2% [7/33] when including a patient with mean GH<2.5µg/L and IGF-1< lower limit of normal). Reductions in the median GH and IGF-1 levels observed at month 3 were maintained up to month 12; the median percent change from baseline to month 12 in GH and IGF-1 levels were -74.71% and -59.33%, respectively. Twenty-nine patients completed the 12-month core phase, 1 withdrew consent, and 3 discontinued treatment due to adverse events (AEs; diabetes mellitus, hyperglycemia, liver function abnormality, n=1 each). Almost all patients (97%; 32/33) experienced AEs; the most common AEs were nasopharyngitis (48.5%), hyperglycemia (42.4%), diabetes mellitus (24.2%), constipation (18.2%), and hypoglycemia (15.2%). Serious AEs were reported in 7 patients with the most common being hyperglycemia (n=2). Long-acting pasireotide demonstrated clinically relevant efficacy and was well tolerated in Japanese patients with acromegaly or pituitary gigantism.

A Phase II Biomarker-Embedded Study of Lapatinib plus Capecitabine as First-line Therapy in Patients with Advanced or Metastatic Gastric Cancer.

An exploratory phase II biomarker-embedded trial (LPT109747; NCT00526669) designed to determine the association of lapatinib-induced fluoropyrimidine gene changes with efficacy of lapatinib plus capecitabine as first-line treatment for advanced gastric cancer or gastroesophageal junction adenocarcinoma independent of tumor HER2 status. Tumor biopsies obtained before and after 7-day lapatinib (1,250 mg) to analyze changes in gene expression, followed by a 14-day course of capecitabine (1,000 mg/m(2) twice daily, 14/21 days) plus lapatinib 1,250 mg daily. Blood samples were acquired for pharmacokinetic analysis. Primary clinical objectives were response rate (RR) and 5-month progression-free survival (PFS). Secondary objectives were overall survival (OS), PFS, time to response, duration of response, toxicity, and identification of associations between lapatinib pharmacokinetics and biomarker endpoints. Primary biomarker objectives were modulation of 5-FU-pathway genes by lapatinib, effects of germline SNPs on treatment outcome, and trough steady-state plasma lapatinib concentrations. Sixty-eight patients were enrolled; (75% gastric cancer, 25% gastroesophageal junction). Twelve patients (17.9%) had confirmed partial response, 31 (46.3%) had stable disease, and 16 (23.9%) had progressive disease. Median PFS and OS were 3.3 and 6.3 months, respectively. Frequent adverse events included diarrhea (45%), decreased appetite (39%), nausea (36%), and fatigue (36%). Lapatinib induced no changes in gene expression from baseline and no significant associations were found for SNPs analyzed. Elevated baseline HER3 mRNA expression was associated with a higher RR (33% vs. 0%; P = 0.008). Lapatinib plus capecitabine was well tolerated, demonstrating modest antitumor activity in patients with advanced gastric cancer. The association of elevated HER3 and RR warrants further investigation as an important player for HER-targeted regimens in combination with capecitabine. Mol Cancer Ther; 15(9); 2251-8. ©2016 AACR.

Lapatinib in Combination With Capecitabine Plus Oxaliplatin in Human Epidermal Growth Factor Receptor 2-Positive Advanced or Metastatic Gastric, Esophageal, or Gastroesophageal Adenocarcinoma: TRIO-013/LOGiC--A Randomized Phase III Trial.

PURPOSE: To evaluate the efficacy of adding lapatinib to capecitabine and oxaliplatin (CapeOx) in patients with previously untreated human epidermal growth factor receptor 2 (HER2) -amplified advanced gastroesophageal adenocarcinoma. PATIENTS AND METHODS: Patients with HER2-positive advanced gastroesophageal adenocarcinoma were randomly assigned at a one-to-one ratio to CapeOx plus lapatinib 1,250 mg or placebo daily. Primary end point was overall survival (OS) in patients with centrally confirmed HER2 amplification in the primary efficacy population. RESULTS: A total of 545 patients were randomly assigned, and 487 patients comprised the primary efficacy population. Median OS in the lapatinib and placebo arms was 12.2 (95% CI, 10.6 to 14.2) and 10.5 months (95% CI, 9.0 to 11.3), respectively, which was not significantly different (hazard ratio, 0.91; 95% CI, 0.73 to 1.12). Median progression-free survival in the lapatinib and placebo arms was 6.0 (95% CI, 5.6 to 7.0) and 5.4 months (95% CI, 4.4 to 5.7), respectively (hazard ratio, 0.82; 95% CI, 0.68 to 1.00; P = .0381). Response rate was significantly higher in the lapatinib arm: 53% (95% CI, 46.4 to 58.8) compared with 39% (95% CI, 32.9 to 45.3) in the placebo arm (P = .0031). Preplanned exploratory subgroup analyses showed OS in the lapatinib arm was prolonged in Asian and younger patients. No correlation was observed between HER2 immunohistochemistry status and survival. There were increased toxicities in the lapatinib arm, particularly diarrhea. CONCLUSION: Addition of lapatinib to CapeOx did not increase OS in patients with HER2-amplified gastroesophageal adenocarcinoma. There were clear differences in the effect of lapatinib depending on region and age. Future studies could examine this correlation.

Lapatinib access into normal brain and brain metastases in patients with Her-2 overexpressing breast cancer.

BACKGROUND: Brain metastases are common in human epidermal growth factor receptor (Her)-2-positive breast cancer. Drug access to brain metastases and normal brain is key to management of cranial disease. In this study, positron emission tomography (PET) scanning after administration of radiolabelled lapatinib was used to obtain direct evidence of cranial drug access. METHODS: Patients with Her-2+ metastatic breast cancer either with at least one 1-cm diameter brain metastasis or without brain metastases underwent dynamic carbon-11 radiolabelled lapatinib ([(11)C]lapatinib)-PET. Less than 20 µg of [(11)C]lapatinib was administered before and after 8 days of oral lapatinib (1,500 mg once daily). Radial arterial blood sampling was performed throughout the 90-min scan. The contribution of blood volume activity to the tissue signal was excluded to calculate lapatinib uptake in normal brain and metastases. Partitioning of radioactivity between plasma and tissue (V T) was calculated and the tissue concentration of lapatinib derived. Plasma lapatinib levels were measured and adverse events noted. RESULTS: Six patients (three with brain metastases) were recruited. About 80% plasma radioactivity corresponded to intact [(11)C]lapatinib after 60 min. PET signal in the brain corresponded to circulating radioactivity levels, with no [(11)C]lapatinib uptake observed in normal brain tissue. In contrast, radioactivity uptake in cranial metastases was significantly higher (p = 0.002) than that could be accounted by circulating radioactivity levels, consistent with [(11)C]lapatinib uptake in brain metastases. There was no difference in lapatinib uptake between the baseline and day 8 scans, suggesting no effect of increased drug access by inhibition of the drug efflux proteins by therapeutic doses of lapatinib. CONCLUSIONS: Increased lapatinib uptake was observed in brain metastases but not in normal brain. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01290354.

Health related quality of life of women in TEACH, a randomised placebo controlled adjuvant trial of lapatinib in early stage Human Epidermal Growth Factor Receptor (HER2) overexpressing breast cancer.

BACKGROUND: To evaluate health related quality of life (HRQOL) in TEACH, a phase III randomized placebo controlled trial of 12 months of adjuvant lapatinib in HER2 positive (HER2+) early breast cancer which demonstrated marginal benefit in disease-free survival. METHODS: Women on TEACH completed the Short Form 36-item health survey (version2; SF-36v2) at the baseline, six and 12 months after therapy initiation and six monthly thereafter. Mean changes were compared between treatment groups for two summary measures (Physical and Mental Component Summary scores; PCS and MCS) and eight domain measures (physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional and mental health), and in patients discontinuing therapy. A five-point change was deemed a Minimally Clinically Important Difference (MCID). Response analysis compared the proportion of patients demonstrating a MCID in HRQOL, and a regression analysis identified predictors of worsening HRQOL. FINDINGS: 3074 (97%) subjects completed baseline SF-36v2. During the initial 12 months, summary SF-36v2 scores decreased in both arms but did not reach Minimally Clinically Important Difference (MCID) despite significant incidences of diarrhoea and rash in lapatinib treated patients. At six months, women receiving lapatinib had more significant reductions (p < 0.01 versus placebo) in social functioning. Early treatment discontinuations were more frequent on lapatinib (32% versus 18%), and were associated with more substantial decrements of HRQOL in both arms. For those discontinuing primarily due to adverse events, decrements in HRQOL reached MCID in Mental Summary scores (MCS) only. Lower baseline HRQOL was a significant predictor of worsening HRQOL (p < 0.05). INTERPRETATION: Despite frequent but usually mild toxicities, adjuvant lapatinib is not associated with clinically significant decreases in overall HRQOL. These placebo-controlled results may also help to inform physicians and patients using lapatinib in metastatic HER2 positive breast cancer. FUNDING: GlaxoSmithKline. The AVON Foundation NY supported PEG, DF and BM and The Friends of the Mater Foundation supported FB.

Phase I Study of Lapatinib and Pemetrexed in the Second-Line Treatment of Advanced or Metastatic Non-Small-Cell Lung Cancer With Assessment of Circulating Cell Free Thymidylate Synthase RNA as a Potential Biomarker.

INTRODUCTION: Lapatinib is a dual tyrosine kinase inhibitor that targets epidermal growth factor receptor and HER2. We report on a dose-escalation study of lapatinib combined with pemetrexed in second-line treatment to evaluate the safety and efficacy in advanced or metastatic non-small-cell lung cancer (NSCLC) and an exploratory study in which circulating cell-free thymidylate synthase ribonucleic acid (cfTSmRNA) was measured in all patients and compared with clinical benefit. PATIENTS AND METHODS: Eligible patients had stage IIIB or IV NSCLC after 1 previous line of chemotherapy and an Eastern Cooperative Oncology Group performance status of 0 to 2. Three dose levels (DLs) of lapatinib (daily)/pemetrexed (every 21 days) were evaluated: DL0, 1250 mg/400 mg; DL1, 1250 mg/500 mg; and DL2, 1500 mg/500 mg, respectively. The primary outcome was identification of the optimal treatment regimen. RESULTS: Eighteen patients were treated (DL0: n = 4; DL1: n = 8; DL2: n = 6). The most common adverse events (any grade) were diarrhea (61%), rash (44%), nausea (33%), anemia, and fatigue (both 28%). DL1 was determined as optimal after 3 dose-limiting toxicities (DLTs) during the first cycle of DL2 (Grade 3 diarrhea and mucositis, Grade 4 lymphocytopenia); no other DLTs were observed. Partial response was detected in 4 patients. cfTSmRNA was at the limit of detection and was not measurable in all patients. Nonsignificant trends were observed, suggesting that higher levels of cfTSmRNA are associated with poorer outcome. Confirmatory studies are required. CONCLUSION: Lapatinib and pemetrexed was well tolerated, and data suggest a similar response rate to pemetrexed monotherapy.

Mild hypothermia facilitates the expression of cold-inducible RNA-binding protein and heat shock protein 70.1 in mouse brain.

An appropriate thermal control system is essential for maintaining brain homeostasis. Hypothermia is a decrease in core body temperature that occurs when the thermoregulatory responses of homeothermic animals are impaired by environmental and situational influences, such as cold ambience and anesthesia. In recent years, hypothermia has been used for medical treatment, i.e., therapeutic hypothermia, for patients with stroke, traumatic brain injury, and heart surgery. However, the target molecules acting during hypothermia have not been identified. To understand the molecular mechanisms, we generated a mouse model of mild hypothermia (1°C-2°C below normal), and analyzed the expression of several genes. After mice were exposed to cold for 24 and 48 h, their rectal temperature reached 33°C-35°C. Then, using real-time quantitative PCR, we analyzed the mRNA expression levels of c-fos, cold-inducible RNA-binding protein (CIRP), heat shock protein (hsp) 70.1, oxytocin, and representative inflammatory cytokines, i.e., tumor necrosis factor (TNF)-α and interleukin (IL)-6 in target organs. Importantly, we found that the expression levels of CIRP and hsp70.1 were elevated in the olfactory bulb within 48 h. In the hypothalamus, CIRP expression levels increased and were followed by an increase in hsp70.1 expression. Meanwhile, TNF-α and IL-6 expression decreased gradually over 24 and 48 h in the olfactory bulb and hypothalamus. These specific expression profiles, i.e., enhanced CIRP and hsp70.1 expression and depressed cytokine expression, suggest that they could regulate apoptosis related to the cytokine signaling.

Cdx1 refines positional identity of the vertebrate hindbrain by directly repressing Mafb expression.

An interplay of transcription factors interprets signalling pathways to define anteroposterior positions along the vertebrate axis. In the hindbrain, these transcription factors prompt the position-appropriate appearance of seven to eight segmental structures, known as rhombomeres (r1-r8). The evolutionarily conserved Cdx caudal-type homeodomain transcription factors help specify the vertebrate trunk and tail but have not been shown to directly regulate hindbrain patterning genes. Mafb (Kreisler, Krml1, valentino), a basic domain leucine zipper transcription factor, is required for development of r5 and r6 and is the first gene to show restricted expression within these two segments. The homeodomain protein vHnf1 (Hnf1b) directly activates Mafb expression. vHnf1 and Mafb share an anterior expression limit at the r4/r5 boundary but vHnf1 expression extends beyond the posterior limit of Mafb and, therefore, cannot establish the posterior Mafb expression boundary. Upon identifying regulatory sequences responsible for posterior Mafb repression, we have used in situ hybridization, immunofluorescence and chromatin immunoprecipitation (ChIP) analyses to determine that Cdx1 directly inhibits early Mafb expression in the neural tube posterior of the r6/r7 boundary, which is the anteriormost boundary of Cdx1 expression in the hindbrain. Cdx1 dependent repression of Mafb is transient. After the 10-somite stage, another mechanism acts to restrict Mafb expression in its normal r5 and r6 domain, even in the absence of Cdx1. Our findings identify Mafb as one of the earliest direct targets of Cdx1 and show that Cdx1 plays a direct role in early hindbrain patterning. Thus, just as Cdx2 and Cdx4 govern the trunk-to-tail transition, Cdx1 may regulate the hindbrain-to-spinal cord transition.

MafB is required for islet beta cell maturation.

Pancreatic endocrine cell differentiation depends on transcription factors that also contribute in adult insulin and glucagon gene expression. Islet cell development was examined in mice lacking MafB, a transcription factor expressed in immature alpha (glucagon(+)) and beta (insulin(+)) cells and capable of activating insulin and glucagon expression in vitro. We observed that MafB(-/-) embryos had reduced numbers of insulin(+) and glucagon(+) cells throughout development, whereas the total number of endocrine cells was unchanged. Moreover, production of insulin(+) cells was delayed until embryonic day (E) 13.5 in mutant mice and coincided with the onset of MafA expression, a MafB-related activator of insulin transcription. MafA expression was only detected in the insulin(+) cell population in MafB mutants, whereas many important regulatory proteins continued to be expressed in insulin(-) beta cells. However, Pdx1, Nkx6.1, and GLUT2 were selectively lost in these insulin-deficient cells between E15.5 and E18.5. MafB appears to directly regulate transcription of these genes, because binding was observed within endogenous control region sequences. These results demonstrate that MafB plays a previously uncharacterized role by regulating transcription of key factors during development that are required for the production of mature alpha and beta cells.

The vHNF1 homeodomain protein establishes early rhombomere identity by direct regulation of Kreisler expression.

The early transcriptional hierarchy that subdivides the vertebrate hindbrain into seven to eight segments, the rhombomeres (r1-r8), is largely unknown. The Kreisler (MafB, Krml1, Val) gene is earliest gene expressed in an r5/r6-restricted manner and is essential for r5 and r6 development. We have identified the S5 regulatory element that directs early Kreisler expression in the future r5/r6 domain in 0-10 somite stage embryos. variant Hepatocyte Nuclear Factor 1 (vHNF1/HNF1beta/LF-3B) is transiently expressed in the r5/r6 domain of 0-10 somite stage embryos and a vHNF1binding site within this element is essential but not sufficient for r5/r6-specific expression. Thus, early inductive events that initiate Kreisler expression are clearly distinct from later-acting ones that modulate its expression levels. This site and some of the surrounding sequences are evolutionarily conserved in the genomic DNA upstream of the Kreisler gene among species as divergent as mouse, humans, and chickens. This provides the first evidence of a direct requirement for vHNF1 in initiation of Kreisler expression, suggests that the role of vHNF1 is evolutionarily conserved, and indicates that vHNF1 collaborates with other transcription factors, which independently bind to the S5 regulatory region, to establish the r5/r6 domain.

Transfection of prion protein gene suppresses coxsackievirus B3 replication in prion protein gene-deficient cells.

The susceptibility of prion protein gene (Prnp)-null cells to coxsackievirus B3 (CVB3) was investigated. Primary cultures of murine Prnp(-/-) brain cells were more sensitive to CVBs than corresponding cells from wild-type mice. The viral susceptibility of a Prnp-null cell line (HpL3-4) derived from the murine hippocampus was compared with that of two established cell lines (HeLa and HEp-2) that are widely employed for CVB3 studies. After infection with CVB3, HpL3-4 cells showed a very rapid and complete cytopathic effect (CPE). CPE developed earlier and viruses replicated at higher titres in HpL3-4 cells compared with HeLa and HEp-2 cells. Under a semi-solid medium, plaques developed rapidly in CVB3-infected HpL3-4 cells. To confirm the effect of Prnp on virus infection, a Prnp(-/-) cell line and a Prnp-transfected neuronal cell line were analysed. The replication and release of infectious particles of CVB3 in Prnp(-/-) cells were significantly more effective than those of the Prnp-transfected cell line. Levels of type I interferon (IFN) after CVB3 infection were higher in the Prnp-transfected cell line than in Prnp(-/-) cells, whereas apoptotic cells were more obvious in the Prnp(-/-) cells than in those of the Prnp-transfected cell line. These findings suggest that the absence of Prnp retards the induction of CVB3-induced IFNs, resulting in an enhanced CVB3 production and apoptotic cell death. Furthermore, our data indicate that the HpL3-4 cell line may provide a novel and sensitive system for isolation of CVB3 from clinical specimens.

The mouse YAF2 gene generates two distinct transcripts and is expressed in pre-and postimplantation embryos.

Mammalian Polycomb group (PcG) proteins are known to function during the maintenance of spatially restricted expression of Hox cluster genes and cellular proliferation. To understand the molecular basis of PcG functions, it is important to identify the components of mammalian PcG complexes. We isolated mouse YAF2 as a protein that interacts with Ring1B, a known constituent of mammalian PcG complexes. We show that the murine YAF2 locus generates two different transcripts, mYAF2-a and mYAF2-b by alternative splicing of the third exons which encode two YAF2 isoforms of 179 and conceptual 60 amino acids, respectively. At least five exons encoding mYAF2 transcripts are mapped on chromosome 15E3 region. Expression of mYAF2 mRNA was observed in both pre- and postimplantation embryos. In mid-gestation embryos, mYAF2 expression is strongly seen in the region close to the surface ectoderm. Finally, biochemical evidence and colocalization studies in tissue culture cells suggest that the product of the mYAF2 gene is involved in PcG complexes together with Ring1B and/or Ring1A.

Involvement of the Polycomb-group gene Ring1B in the specification of the anterior-posterior axis in mice.

The products of the Polycomb group of genes form complexes that maintain the state of transcriptional repression of several genes with relevance to development and in cell proliferation. We have identified Ring1B, the product of the Ring1B gene (Rnf2 - Mouse Genome Informatics), by means of its interaction with the Polycomb group protein Mel18. We describe biochemical and genetic studies directed to understand the biological role of Ring1B. Immunoprecipitation studies indicate that Ring1B form part of protein complexes containing the products of other Polycomb group genes, such as Rae28/Mph1 and M33, and that this complexes associate to chromosomal DNA. We have generated a mouse line bearing a hypomorphic Ring1B allele, which shows posterior homeotic transformations of the axial skeleton and a mild derepression of some Hox genes (Hoxb4, Hoxb6 and Hoxb8) in cells anterior to their normal boundaries of expression in the mesodermal compartment. By contrast, the overexpression of Ring1B in chick embryos results in the repression of Hoxb9 expression in the neural tube. These results, together with the genetic interactions observed in compound Ring1B/Mel18 mutant mice, are consistent with a role for Ring1B in the regulation of Hox gene expression by Polycomb group complexes.