A human sex-chromosomal gene family expressed in male germ cells and encoding variably charged proteins.
Approximately 12 X-Y homologous gene pairs have been identified in the non-recombining portions of human sex chromosomes. These X-Y gene pairs fall into two categories. In the first category, both X and Y homologs are ubiquitously expressed. In the second category, the X homolog is ubiquitously expressed, whereas the Y homolog is expressed exclusively in the testis. Here we describe a family of human X-Y genes that cannot be assigned to either category. Designated VCX / Y ( Variable Charge X / Y; VCY previously known as BPY1 ), this gene family has multiple members on both X and Y, and all appear to be expressed exclusively in male germ cells. Members of the VCX / Y family share a high degree of sequence identity, with the exception that a 30 nucleotide unit is tandemly repeated in X-linked members but is present only once in Y-linked members. These atypical features suggest that the VCX / Y family has evolved in a manner previously unrecognized for mammalian X-Y genes. We also found that a copy of VCX is present in CRI-S232, a previously described genomic fragment derived from the X chromosome. Studies have shown that aberrant recombination between arrays of CRI-S232-homologous repeats flanking the steroid sulfatase ( STS ) gene results in STS deletion, which is manifested clinically as X-linked ichthyosis. The revelation that CRI-S232 contains VCX offers a more precise description of the genetic etiology of X-linked ichthyosis: it results from aberrant recombination between VCX gene arrays that flank the STS locus.
Lahn
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Howard Hughes Medical Institute, Whitehead Institute and Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, MA 02142, USA. blahn@genetics-uchicago.edu
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D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D010375:Pedigree; D013094:Spermatozoa / Q000378:metabolism*; D014960:X Chromosome / Q000235:genetics*; D014998:Y Chromosome / Q000235:genetics*
D009687:Nuclear Proteins; C404411:VCX protein, human; C404412:VCY protein, human