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Expression profiles for six zebrafish genes during gonadal sex differentiation.

Jørgensen A, Morthorst JE, Andersen O, Rasmussen LJ, Bjerregaard P - Reprod. Biol. Endocrinol. (2008)

Bottom Line: 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.When comparing all five genes with expected sex related expression 56% show expression expected for either male or female.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark. annejoer@ruc.dk

ABSTRACT

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.

Conclusion: 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.

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Expression of androgen receptor (ar) in whole juvenile zebrafish homogenate during sex determination and differentiation. Values are expressed as arbitrary units of ar expression levels normalised against the expression levels of β-actin amplified from the same template. * indicate significant difference (p < 0.05) after Tukey test compared to the day before in the high expresser group. There was always significant difference between the high and low expresser group (p < 0.05) after Tukey test.
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Figure 2: Expression of androgen receptor (ar) in whole juvenile zebrafish homogenate during sex determination and differentiation. Values are expressed as arbitrary units of ar expression levels normalised against the expression levels of β-actin amplified from the same template. * indicate significant difference (p < 0.05) after Tukey test compared to the day before in the high expresser group. There was always significant difference between the high and low expresser group (p < 0.05) after Tukey test.

Mentions: The expression levels of ar were low for both the high and low expresser group during the first period (2–8 dph) (Figure 2), however, with two distinct groups of high and low expressers. The ar expression has a peak at 16 dph, which is significantly different (p < 0.05) compared to the expression on the day before. The ar expression reaches the highest level at 22 dph for the high-expresser group, also significantly different (p < 0.05) from the expression on the day before. The 22 dph peak corresponds to the time period right after the bipotential gonad is starting to differentiate into ovary or testes. In the low expresser group no increase in ar levels was seen. In the period 19–20 dph there is a marked decrease in the expression level for the high-expresser group, which coincides with the time of juvenile ovary-to-testes transformation in zebrafish.


Expression profiles for six zebrafish genes during gonadal sex differentiation.

Jørgensen A, Morthorst JE, Andersen O, Rasmussen LJ, Bjerregaard P - Reprod. Biol. Endocrinol. (2008)

Expression of androgen receptor (ar) in whole juvenile zebrafish homogenate during sex determination and differentiation. Values are expressed as arbitrary units of ar expression levels normalised against the expression levels of β-actin amplified from the same template. * indicate significant difference (p < 0.05) after Tukey test compared to the day before in the high expresser group. There was always significant difference between the high and low expresser group (p < 0.05) after Tukey test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2500022&req=5

Figure 2: Expression of androgen receptor (ar) in whole juvenile zebrafish homogenate during sex determination and differentiation. Values are expressed as arbitrary units of ar expression levels normalised against the expression levels of β-actin amplified from the same template. * indicate significant difference (p < 0.05) after Tukey test compared to the day before in the high expresser group. There was always significant difference between the high and low expresser group (p < 0.05) after Tukey test.
Mentions: The expression levels of ar were low for both the high and low expresser group during the first period (2–8 dph) (Figure 2), however, with two distinct groups of high and low expressers. The ar expression has a peak at 16 dph, which is significantly different (p < 0.05) compared to the expression on the day before. The ar expression reaches the highest level at 22 dph for the high-expresser group, also significantly different (p < 0.05) from the expression on the day before. The 22 dph peak corresponds to the time period right after the bipotential gonad is starting to differentiate into ovary or testes. In the low expresser group no increase in ar levels was seen. In the period 19–20 dph there is a marked decrease in the expression level for the high-expresser group, which coincides with the time of juvenile ovary-to-testes transformation in zebrafish.

Bottom Line: 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.When comparing all five genes with expected sex related expression 56% show expression expected for either male or female.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark. annejoer@ruc.dk

ABSTRACT

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.

Conclusion: 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.

Show MeSH