Two Sox9 Genes on Duplicated Zebrafish Chromosomes: Expression of Similar Transcription Activators in Distinct Sites

Abstract

Sox9 is a transcription factor required for cartilage formation and testis determination in mammals. We have cloned from zebrafish two sox9 genes, termed sox9a and sox9b. Gene phylogenies showed that both genes are orthologous to tetrapod SOX9 genes. Genetic mapping showed that these two loci reside on chromosome segments that were apparently duplicated in a large-scale genomic duplication event in ray fin fish phylogeny. Both Sox9a and Sox9b proteins bind to the HMG consensus DNA sequences in vitro. We tested different domains for transactivation potential and identified a potential activation domain located in the middle of both Sox9a and Sox9b. During embryogenesis, sox9a and sox9b expression patterns are distinct but overlap in some regions of the brain, head skeleton, and fins. Expression of sox9a/b correlates well with that of col2a1 in chondrogenic elements. In the adults, sox9a is expressed in many tissues including brain, muscle, fin, and testis, whereas sox9b expression is restricted to previtellogenic oocytes of the ovary. This expression pattern predicts that sox9a and sox9b may have unique functions in some specific tissues during development. The role of gene duplication for the evolution of developmental gene function is discussed.

Cloning and sequence analysis of Sox genes in a tetraploid cyprinid fish, Tor douronensis

“…Our analysis shows that Sox genes of Tor douronensis (Sox4, Sox9, Sox14 and Sox21) have 2 to 4 copies compared to mammals, and the pattern was also observed in other teleost fishes [4,5,43] . A large number of duplicated copies of single copy mammalian genes have been identified in teleost fishes.…”

Sexual dimorphic expression of DMRT1 and Sox9a during gonadal differentiation and hormone‐induced sex reversal in the teleost fish Nile tilapia (Oreochromis niloticus)

“…As for teleosts, it was reported that two types of Sox9 were reported as Sox9a and Sox9b/a2 (Zebrafish, Chiang et al, 2001;medaka, Nakamoto et al, 2005). However, testisdominant type of Sox9 was different in each species (Zebrafish, tilapia, Sox9a; medaka, Sox9b/a2).…”

Molecular mechanisms underlying sex change in hermaphroditic groupers

“…SOX9, the direct target of Sry, plays a critical role in testis determination in mammals (Foster et al 1994). Two SOX9 genes, termed SOX9a and SOX9b, have been identified in zebrafish (Chiang et al 2001), but whether SOX9a and/or SOX9b are involved in sex determination or differentiation has so far not been studied . In orangespotted groupers, we cloned a 252 bp fragment of SOX9 and produced a specific antibody.…”