Retroposition of autosomal mRNA yielded testis-specific gene family on
human Y chromosome
Bruce T Lahn
& David C Page
Howard Hughes Medical Institute, Whitehead Institute
and Department of Biology, Massachusetts Institute of Technology,
9 Cambridge Center, Cambridge, Massachusetts
02142, USA.
Correspondence should be addressed to David C Page dcpage@wi.mit.edu
Most genes in the human NRY (non-recombining portion of the Y chromosome)
can be assigned to one of two groups: X-homologous genes or testis-specific
gene families with no obvious X-chromosomal homologues1,
2.
The CDY genes have been localized to the human Y chromosome1,
and we report here that they are derivatives of a conventional single-copy
gene, CDYL (CDY-like), located on human chromosome 13 and mouse
chromosome 6. CDY genes retain CDYL exonic sequences but lack
its introns. In mice, whose evolutionary lineage diverged before the appearance
of the Y-linked derivatives, the autosomal Cdyl gene produces two transcripts;
one is expressed ubiquitously and the other is expressed in testes only. In
humans, autosomal CDYL produces only the ubiquitous transcript; the
testis-specific transcript is the province of the Y-borne CDY genes.
Our data indicate that CDY genes arose during primate evolution by
retroposition of a CDYL mRNA and amplification of the retroposed gene.
Retroposition contributed to the gene content of the human Y chromosome, together
with two other molecular evolutionary processes: persistence of a subset of
genes shared with the X chromosome3,
4 and transposition of
genomic DNA harbouring intact transcription units5.
