R. Ivell et al., Progressive inactivation of the haploid expressed gene for the sperm-specific endozepine-like peptide (ELP) through primate evolution, GENE, 255(2), 2000, pp. 335-345
The endozepine-like peptide (ELP) is a novel intracellular molecule which i
s expressed in high amounts at both mRNA and protein levels very specifical
ly in late haploid male germ cells. It is closely related to the ubiquitous
acyl-CoA binding protein, is highly conserved, shares a similar ability to
bind mid-long chain acyl-CoA, and is thus likely to be involved in mature
sperm metabolism While it has been characterized from diverse mammals, it h
as so far not been possible to identify an equivalent molecule in the prima
te testis. Using a PCR approach, combined with cDNA cloning and Northern hy
bridization, testicular transcripts and/or genomic DNA were analysed for di
fferent primate species, including human. In the marmoset and cynomolgus ma
caque normally structured transcripts appear to be expressed, though at a l
ow level. In the human testis, two ran transcripts were characterized, hELP
1 and hELP2, the products of independent duplicated genes. Both transcripts
were longer than in nonmammalian species, included frame-shift mutations a
nd substantial sequence insertions, preventing the translation of a sensibl
e protein. Genomic PCR analysis of three anthropoid species, chimpanzee, go
rilla and orangutan, showed the presence of a similarly mutated hELP1 gene.
Only in the gorilla was a hELP2 gene identified, apparently lacking the Fr
ame-shift mutation, and thus potentially able to give rise to a functional
ELF protein. Taken together, these results show that during primate evoluti
on there has been a progressive inactivation of the ELF gene, initially wit
h a down-regulation in lower primates, and subsequently with inactivating m
utations in the open reading frame. At some time during simian evolution pr
ior to these mutations there has been a gene duplication, though this secon
d gene has also become inactivated in humans. In its pattern of evolution t
he ELF gene shows similarities with the MDC/fertilin family, whose members
are also considered essential components of haploid sperm in non-primates,
but which are progressively inactivated in anthropoids and humans. We shoul
d like to speculate that the established subfertility of the human male may
not be a recent event, but the consequence of a longer evolutionary proces
s whereby primates have traded off absolute fertility against social or sex
ual advantages. (C) 2000 Elsevier Science B.V. All rights reserved.