Sexually dimorphic expression of the sex chromosome-linked genes cntfa and pdlim3a in the medaka brain.
In vertebrates, sex differences in the brain have been attributed to differences in gonadal hormone secretion; however, recent evidence in mammals and birds shows that sex chromosome-linked genes, independent of gonadal hormones, also mediate sex differences in the brain. In this study, we searched for genes that were differentially expressed between the sexes in the brain of a teleost fish, medaka (Oryzias latipes), and identified two sex chromosome genes with male-biased expression, cntfa (encoding ciliary neurotrophic factor a) and pdlim3a (encoding PDZ and LIM domain 3 a). These genes were found to be located 3-4 Mb from and on opposite sides of the Y chromosome-specific region containing the sex-determining gene (the medaka X and Y chromosomes are genetically identical, differing only in this region). The male-biased expression of both genes was evident prior to the onset of sexual maturity. Sex-reversed XY females, as well as wild-type XY males, had more pronounced expression of these genes than XX males and XX females, indicating that the Y allele confers higher expression than the X allele for both genes. In addition, their expression was affected to some extent by sex steroid hormones, thereby possibly serving as focal points of the crosstalk between the genetic and hormonal pathways underlying brain sex differences. Given that sex chromosomes of lower vertebrates, including teleost fish, have evolved independently in different genera or species, sex chromosome genes with sexually dimorphic expression in the brain may contribute to genus- or species-specific sex differences in a variety of traits.
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan.
Sayaka
S
Maehiro
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Akio
A
Takeuchi
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Junpei
J
Yamashita
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Towako
T
Hiraki
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Yukika
Y
Kawabata
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Kiyoshi
K
Nakasone
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan.
Kohei
K
Hosono
Division of Reproductive Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan.
Takeshi
T
Usami
Division of Reproductive Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan.
Bindhu
B
Paul-Prasanth
Division of Reproductive Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan; Institution for Collaborative Relations, Ehime University, Matsuyama, Ehime 790-8577, Japan.
Yoshitaka
Y
Nagahama
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan.
Yoshitaka
Y
Oka
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan. Electronic address: okubo@marine.fs.a.u-tokyo.ac.jp.
Kataaki
K
Okubo
D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D020934:Ciliary Neurotrophic Factor / Q000145:classification / Q000235:genetics*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D029941:Fish Proteins / Q000235:genetics*; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D008040:Genetic Linkage; D008297:Male; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D009990:Oryzias / Q000235:genetics*; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012737:Sex Factors; D013739:Testosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors; D014998:Y Chromosome / Q000235:genetics*
D020934:Ciliary Neurotrophic Factor; D029941:Fish Proteins; D013739:Testosterone; D004958:Estradiol; C003600:11-ketotestosterone
Brain; Medaka; Sex chromosome; Sex differences; cntf; pdlim3