An immune-related gene evolved into the master sex-determining gene in rainbow trout, Oncorhynchus mykiss.
Since the discovery of Sry in mammals [1, 2], few other master sex-determining genes have been identified in vertebrates [3-7]. To date, all of these genes have been characterized as well-known factors in the sex differentiation pathway, suggesting that the same subset of genes have been repeatedly and independently selected throughout evolution as master sex determinants [8, 9]. Here, we characterized in rainbow trout an unknown gene expressed only in the testis, with a predominant expression during testicular differentiation. This gene is a male-specific genomic sequence that is colocalized along with the sex-determining locus. This gene, named sdY for sexually dimorphic on the Y chromosome, encodes a protein that displays similarity to the C-terminal domain of interferon regulatory factor 9. The targeted inactivation of sdY in males using zinc-finger nuclease induces ovarian differentiation, and the overexpression of sdY in females using additive transgenesis induces testicular differentiation. Together, these results demonstrate that sdY is a novel vertebrate master sex-determining gene not related to any known sex-differentiating gene. These findings highlight an unexpected evolutionary plasticity in vertebrate sex determination through the demonstration that master sex determinants can arise from the de novo evolution of genes that have not been previously implicated in sex differentiation.
INRA, UR1037, LPGP, Fish Physiology and Genomics, 35000 Rennes, France.
Ayaka
A
Yano
René
R
Guyomard
Barbara
B
Nicol
Elodie
E
Jouanno
Edwige
E
Quillet
Christophe
C
Klopp
Cédric
C
Cabau
Olivier
O
Bouchez
Alexis
A
Fostier
Yann
Y
Guiguen
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005260:Female; D050835:Interferon Regulatory Factors / Q000235:genetics; D008297:Male; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000254:growth & development / Q000276:immunology; D012689:Sequence Homology, Nucleic Acid; D019849:Sex Determination Processes; D013737:Testis / Q000254:growth & development* / Q000378:metabolism; D014998:Y Chromosome / Q000235:genetics
D050835:Interferon Regulatory Factors