RESUMO
C15orf2 (Chromosome 15 open reading frame 2) is an intronless gene, which is located in the Prader-Willi syndrome (PWS) chromosomal region on human chromosome 15. Mice do not have an orthologous gene. Here we show that expression of C15orf2 in the fetal human brain is imprinted. Using Western blot and immunohistological studies we have obtained evidence that C15orf2 protein is present in several regions of the brain. Previously published phylogenetic studies as well as population genetic studies based on complex haplotypes as described here suggest that C15orf2 is under positive Darwinian selection. These results indicate that C15orf2 might have an important role in human biology and that a deficiency of C15orf2 might contribute to PWS.
Assuntos
Cromossomos Humanos Par 15/genética , Impressão Genômica , Proteínas do Tecido Nervoso/genética , Fases de Leitura Aberta , Síndrome de Prader-Willi/genética , Seleção Genética , Alelos , Animais , Linhagem Celular , Haplótipos , Humanos , Hipotálamo/citologia , Hipotálamo/metabolismo , Camundongos , Proteínas do Tecido Nervoso/metabolismo , Complexo de Proteínas Formadoras de Poros Nucleares , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Sequence analysis of the imprinted UBE3A gene in a 3-year-old girl suspected of having Angelman syndrome had revealed a de novo 3bp in frame deletion predicted to encode a protein lacking the amino acid G538 (based on sequence NM_130838). In order to assess the clinical relevance of this unknown variant, we determined the parental origin and the functional consequences of the deletion. We separated the two chromosomes 15 by microdissection of metaphase spreads and used cytogenetic and molecular markers to demonstrate that the deletion is on the maternal chromosome. For determining the functional consequences of the deletion, we modelled the structure of the deletion mutant based on the wildtype X-ray structure and simulated the molecular dynamics of the wildtype and mutant protein in complex with UcbH7. Our simulations showed that deletion of G538 destroys a network of salt bridges between highly conserved residues in the catalytic cleft of UBE3A. In conclusion, our results strongly suggest that the 3bp deletion is a loss-of-function mutation of the maternal UBE3A allele that has caused Angelman syndrome in our patient. Our study may serve as a paradigm to determine the parental origin of a de novo mutation.
Assuntos
Síndrome de Angelman/genética , Predisposição Genética para Doença/genética , Mutação , Ubiquitina-Proteína Ligases/genética , Adulto , Síndrome de Angelman/diagnóstico , Sequência de Bases , Pré-Escolar , Deleção Cromossômica , Cromossomos Humanos Par 15/genética , Cristalografia por Raios X , Saúde da Família , Feminino , Humanos , Masculino , Modelos Moleculares , Dados de Sequência Molecular , Pais , Conformação Proteica , Deleção de Sequência , Ubiquitina-Proteína Ligases/químicaRESUMO
The imprinted domain in human 15q11-q13 is controlled by a bipartite imprinting centre (IC), which overlaps the 5' part of the paternally expressed SNURF-SNRPN gene. We have recently described two novel genes upstream of SNURF-SNRPN (PWRN1 and PWRN2), which are biallelically expressed in the testis. We have now found that PWRN1 represents an alternative 5' part of SNURF-SNRPN, and that its expression in the brain is imprinted. To determine when the locus is activated during spermatogenesis and which factors are involved in this process, we have mined gene-expression data of testicular biopsies from men with different types of spermatogenic failure. Whereas PWRN1-SNURF-SNRPN and PWRN2 are expressed in post-meiotic germ cells only, a hitherto undetected SNURF-SNRPN upstream transcript is expressed already at meiosis. Several epigenetic factors (eg, MBD1 and MBD2 isoforms, MBD3L1, SUVH39H2, BRDT, and EZH2) are upregulated at specific stages of spermatogenesis, suggesting that they play an important role in the epigenetic reprogramming during spermatogenesis.
Assuntos
Epigênese Genética , Genes Reguladores , Proteínas Nucleares/genética , Espermatogênese/genética , Proteínas Centrais de snRNP/genética , Processamento Alternativo , Cromossomos Humanos Par 15 , Proteínas de Ligação a DNA/genética , Expressão Gênica , Impressão Genômica , Humanos , Masculino , RNA Mensageiro/metabolismo , Proteínas Repressoras/metabolismo , Testículo/metabolismoRESUMO
The Prader-Willi syndrome (PWS) region contains several genes transcribed from the paternal chromosome only. We have previously identified a testis-specific gene, C15orf2, which maps between NDN and SNURF-SNRPN and is expressed from both alleles. Here we report on two novel genes (prader-willi region non-protein-coding RNA 1 and 2) located between NDN and C15orf2. By database search we found five partially duplicated copies, of which only one of each appears to be active. PWRN2 is expressed only in testis and is biallelic. PWRN1 is biallelically expressed in testis and kidney, but monoallelically in fetal brain. Methylation analysis of a CpG island 15 kb upstream of exon 1 showed absence of methylation in spermatozoa, but methylated and unmethylated alleles in fetal brain. Reinvestigation of C15orf2 revealed that this gene is also expressed in fetal brain and that expression in this tissue is monoallelic. We conclude that PWRN1 and C15orf2 may play a role in PWS.