Role of the transcriptional corepressor Bcor in embryonic stem cell differentiation and early embryonic development

Bcor (BCL6 corepressor) is a widely expressed gene that is mutated in patients with X-linked Oculofaciocardiodental (OFCD) syndrome. BCOR regulates gene expression in association with a complex of proteins capable of epigenetic modification of chromatin. These include Polycomb group (PcG) proteins, Skp-Cullin-F-box (SCF) ubiquitin ligase components and a Jumonji C (Jmjc) domain containing histone demethylase. To model OFCD in mice and dissect the role of Bcor in development we have characterized two loss of function Bcor alleles. We find that Bcor loss of function results in a strong parent-of-origin effect, most likely indicating a requirement for Bcor in extraembryonic development. Using Bcor loss of function embryonic stem (ES) cells and in vitro differentiation assays, we demonstrate that Bcor plays a role in the regulation of gene expression very early in the differentiation of ES cells into ectoderm, mesoderm and downstream hematopoietic lineages. Normal expression of affected genes (Oct3/4, Nanog, Fgf5, Bmp4, Brachyury and Flk1) is restored upon re-expression of Bcor. Consistent with these ES cell results, chimeric animals generated with the same loss of function Bcor alleles show a low contribution to B and T cells and erythrocytes and have kinked and shortened tails, consistent with reduced Brachyury expression. Together these results suggest that Bcor plays a role in differentiation of multiple tissue lineages during early embryonic development.     

A novel deletion mutation,c.1296delT in the BCOR gene,is associated with oculo-facio-cardio-dental syndrome

The purpose of the present study was to analyze the clinical phenotypes of a girl with oculo-facio-cardio-dental(OFCD)syndrome and to identify the potential pathogenic mutation responsible for her disease. The patient underwent detailed clinical examinations and phenotype data were collected over a follow-up period of 9 years. Mutation analysis of the candidate gene BCOR was performed with polymerase chain reaction and Sanger sequencing. BCOR of 60 unrelated normal individuals were also sequenced as a control group. Clinical phenotyping and follow-up study results indicate that this patient had multiple system anomalies including ocular, facial, cardiac, dental, and limb malformations. In addition, papilloma of the choroid plexus was identified, which represents the first report of this phenotype in an OFCD patient. A novel deletion mutation, c.1296 delT in exon4 of the BCOR gene, was identified in this patient and was not found in her parents or in 60 normal unrelated individuals. This deletion was a frameshift mutation and is proposed to encode a premature stop codon, thus producing a truncated protein. Our patient fitted the diagnostic criteria for OFCD syndrome and we report the first papilloma of the choroid plexus in an OFCD patient, expanding the recognized phenotypic spectrum of this disease. Meanwhile, we identified a novel deletion mutation that may cause OFCD syndrome.     

两个保守的snoRNA基因SNORA50和SNORA71在灵长类和啮齿类的转录活性及组织表达谱

核仁小分子RNA（small nucleolar RNA,snoRNA）的主要功能是参与rRNA的修饰。最近研究表明,snoRNA可能具有广泛的生物学功能。大部分snoRNA比较保守,但也有一些snoRNA基因具有种属特异性。有意义的是,该研究发现,基因序列高度保守的snoRNA（SNORA50和SNORA71）呈现物种特异性的组织表达谱。SNORA50位于Cnot1基因内含子中,在脊椎动物中高度保守。表达谱分析发现,SNORA50在灵长类（人和恒河猴）和鸟类（鸡）的各种组织中广泛表达,但在正常发育的小鼠组织中检测不到。SNORA71位于一个非编码RNA基因snhg11的内含子中,在哺乳动物中比较保守。研究发现,SNORA71在灵长类各种组织广泛表达,而小鼠中主要在脑组织表达,与宿主基因snhg11表达谱一致。随小鼠脑发育过程的进展,SNORA71表达水平逐渐上调,提示其参与小鼠脑发育的调控。而在恒河猴从胚胎到成体的脑发育过程中,SNORA71表达没有显著的改变。这些结果表明,SNORA71对灵长类和啮齿类的神经发育可能存在不同的调控模式。基因序列保守的SNORA50和SNORA71呈现物种特异的表达模式,说明snoRNA在个体发育和系统进化中都发挥着重要的调控功能。     

Localization of lysosomal acid phosphatase mRNA in mouse tissues.

We studied the expression of lysosomal acid phosphatase (LAP) in mouse by hybridizing Northern blots and tissue sections with the mouse LAP cDNA. Three mRNA species of 2.3, 3.2 and 5.2 KB were identified, which differ in the length of their 3' untranslated region (UTR). The 3.2 KB mRNA is expressed in equal amounts in all tissues and represents the major species in most tissues, whereas the amounts of the 2.3 and 5.2 KB species differ. In situ hybridization of different tissues of adult mice showed a uniform expression of LAP, as expected for a housekeeping gene, except in testis and brain. In testis we found an increase in the LAP mRNA level in spermatocytes. By Northern blot analysis of young mouse testis, this increase could be attributed to late pachytene primary spermatocytes or secondary spermatocytes. In brain tissue the neurons were predominantly labeled, especially the Purkinje and pyramidal cells, whereas glial cells expressed only low amounts of LAP mRNA. Very high LAP expression was also found in the epithelial cells of the choroid plexus. Analysis of LAP expression during mouse embryonic development between Days 9.5 and 17.5 revealed a prominent expression relative to other tissues in the neural tube from Day 9.5 to Day 13.5.