Expression profiles for six zebrafish genes during gonadal sex differentiation.
BACKGROUND
The mechanism of sex determination in zebrafish is largely unknown and neither sex chromosomes nor a sex-determining gene have been identified. This indicates that sex determination in zebrafish is mediated by genetic signals from autosomal genes. The aim of this study was to determine the precise timing of expression of six genes previously suggested to be associated with sex differentiation in zebrafish. The current study investigates the expression of all six genes in the same individual fish with extensive sampling dates during sex determination and -differentiation.


RESULTS
In the present study, we have used quantitative real-time PCR to investigate the expression of ar, sox9a, dmrt1, fig alpha, cyp19a1a and cyp19a1b during the expected sex determination and gonadal sex differentiation period. The expression of the genes expected to be high in males (ar, sox9a and dmrt1a) and high in females (fig alpha and cyp19a1a) was segregated in two groups with more than 10 times difference in expression levels. All of the investigated genes showed peaks in expression levels during the time of sex determination and gonadal sex differentiation. Expression of all genes was investigated on cDNA from the same fish allowing comparison of the high and low expressers of genes that are expected to be highest expressed in either males or females. There were 78% high or low expressers of all three "male" genes (ar, sox9a and dmrt1) in the investigated period and 81% were high or low expressers of both "female" genes (fig alpha and cyp19a1a). When comparing all five genes with expected sex related expression 56% show expression expected for either male or female. Furthermore, the expression of all genes was investigated in different tissue of adult male and female zebrafish.


CONCLUSIONS
In zebrafish, the first significant peak in gene expression during the investigated period (2-40 dph) was dmrt1 at 10 dph which indicates involvement of this gene in the early gonadal sex differentiation of males.
Jørgensen
Anne
A
Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark. annejoer@ruc.dk
Morthorst
Jane E
JE
Andersen
Ole
O
Rasmussen
Lene J
LJ
Bjerregaard
Poul
P
D000818:Animals; D001141:Aromatase / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D006066:Gonads / Q000196:embryology* / Q000502:physiology; D024002:HMGB Proteins / Q000235:genetics; D008297:Male; D009928:Organ Specificity; D011944:Receptors, Androgen / Q000235:genetics; D055758:SOX9 Transcription Factor; D012733:Sex Differentiation / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics
D001141:Aromatase; D051792:Basic Helix-Loop-Helix Proteins; D005819:Genetic Markers; D024002:HMGB Proteins; D011944:Receptors, Androgen; D055758:SOX9 Transcription Factor; D014157:Transcription Factors; D029961:Zebrafish Proteins; C110547:DMRT1 protein; C109920:Figla protein, mouse; C504918:Sox9a protein, zebrafish; C440729:Cyp19a1a protein, zebrafish; C440728:Cyp19a1b protein, zebrafish