Evolution of the DAZ gene family suggests that Y-linked DAZ plays little, or a limited, role in spermatogenesis but underlines a recent African origin for human populations.
The recent transposition to the Y chromosome of the autosomal DAZL1 gene, potentially involved in germ cell development, created a unique opportunity to study the rate of Y chromosome evolution and assess the selective forces that may act upon such genes, and provided a new estimate of the male-to-female mutation rate (alpham). Two different Y-located DAZ sequences were observed in all Old World monkeys, apes and humans. Different DAZ copies originate from independent amplification events in each primate lineage. A comparison of autosomal DAZL1 and Y-linked DAZ intron sequences gave a new figure for male-to-female mutation rates of alpham = 4. It was found that human DAZ exons and introns are evolving at the same rate, implying neutral genetic drift and the absence of any functional selective pressures. We therefore hypothesize that Y-linked DAZ plays little, or a limited, role in human spermatogenesis. The two copies of DAZ in man appear to be due to a relatively recent duplication event (55 000-200 000 years). A worldwide survey of 67 men from five continents representing 19 distinct populations showed that most males have both DAZ variants. This implies a common origin for the Y chromosome consistent with a recent 'out of Africa' origin of the human race.
Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA.
A I
AI
Agulnik
A
A
Zharkikh
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H
Boettger-Tong
T
T
Bourgeron
K
K
McElreavey
C E
CE
Bishop
D000349:Africa; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002520:Cercopithecidae / Q000235:genetics; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D004251:DNA Transposable Elements; D000075364:Deleted in Azoospermia 1 Protein; D005260:Female; D008040:Genetic Linkage; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008957:Models, Genetic; D005810:Multigene Family; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011323:Primates / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics*; D013091:Spermatogenesis / Q000235:genetics*; D014998:Y Chromosome / Q000235:genetics*
C095668:DAZ1 protein, human; D017931:DNA Primers; D004251:DNA Transposable Elements; D000075364:Deleted in Azoospermia 1 Protein; D016601:RNA-Binding Proteins