Degree of Sex Differentiation of Genetic Female Chicken Treated with Different Doses of an Aromatase Inhibitor

Abstract

Injection of an aromatase inhibitor before gonadal sex differentiation can induce female-to-male sex reversal in chicken, but a higher dose could reduce hatchability. In the present study, the dosage effect of Fadrozole, a nonsteroidal aromatase inhibitor, on gonadal differentiation was analyzed in sex-reversed genetic female chicken. There was no significant difference for the hatchability among low-dose (0.1, 0.3 and 0.5 mg) Fadrozole-injected groups and control groups (p > 0.05), but in high-dose groups (1.0 mg and 1.3 mg) the hatchability was significantly reduced (p < 0.05). Complete phenotypic sex reversal was observed in both high- and low- dose groups, with more than 90% of genetic females reversed into phenotypic male chicks. The degree of gonadal differentiation in 124 chicken at 30 weeks of age was classified into 5 categories according to the visual appearance and histological structure of the gonads. Category I and V were standard ovary and testis, respectively, while category II, III, and IV represented gonads of slightly, moderately, and highly sex-reversed females, respectively. Most gonads in low-dose groups were classified into category I, II, and III, while those in high-dose groups were mainly category IV. The serum testosterone levels in the 1.3 mg group were significantly higher and the estradiol levels lower than those in low-dose groups (p < 0.05). In conclusion, the range from 0.5 to 1.0 mg Fadrozole is a key interval for survival of chicken embryos. The gonadal differentiation in sex-reversed females at 30 weeks of age is highly dependent on the dose of Fadrozole injected prior to gonadal sex differentiation.

Differential Development of Sex-related Characters of Chickens from the GSP and PNP/DO Inbred Lines after Left Ovariectomy

“…Several reports have indicated that the different degrees of sex reversal of genetic females using either chemical treatment or left-ovariectomy mainly depends on the individuals [15,23,24]. However, the present study showed consistent degrees of masculinization for the respective inbred line of chicken, indicating that differences in genetic background may play a role in response to induced sex reversal.…”

The Molecular Genetics of Ovarian Differentiation in the Avian Model

“…Ablation of this gene in somatic cells does not affect the ability of cells to enter meiosis, even though somatic cell differentiation was affected [Liu et al, 2008], supporting the idea that the role of ␤ -catenin in germ cells is independent of its effects in somatic cells. Interestingly, while RSPO1 promotes germ cell proliferation in XX mouse gonads [Yang et al, 2008;Chassot et al, 2011], most germ cells survive until birth in this KO, which is different to Wnt4 KO mice (as mentioned above). Therefore, it has been suggested that a basal level of WNT4 found in both XX and XY gonads, and that is independent of RSPO1 [Chassot et al, 2008a], may have an additional role in germ cell survival [Chassot et al, 2008b].…”

“…Thus, WNT4 appears to be important for both sexual identity and survival of the female germ cells. Like Wnt4 , loss of Rspo1 leads to the failure of XX germ cells to enter meiosis [Yang et al, 2008;Chassot et al, 2011], with some of these cells adopting male characteristics, at a stage where no significant sex reversal is seen in the somatic cells [Chassot et al, 2008b[Chassot et al, , 2011. WNT4 and RSPO1 probably act on germ cells through activation of ␤ -catenin production, which is itself essential for survival of the meiotic germ cells [Liu et al, 2008].…”

Methylation Status of cMHM and Expression of Sex-Specific Genes in Adult Sex-Reversed Female Chickens

“…2003; Yang et al, 2008]. Possible reasons for the infertility of sex-reversed hens are the reduced motility of spermatozoa, high oligospermy or an abnormal development of the vasa deferentia [Abinawanto et al, 1998;Vaillant et al, 2003].…”

“…The ratio between androgen and estrogen, rather than their absolute levels, is important for spermatogenesis [Sharpe, 1998;Rivas et al, 2002;Akingbemi, 2005]. A previous study suggested that the natural logarithm (ln) of the ratio of testosterone and estradiol in serum is well-related to the degree of gonadal sex differentiation [Yang et al, 2008]. To date, avian sex-specific genes, including P450arom (CYP19A1) , estrogen receptor alpha (ER ␣ ) , forkhead transcription factor (FOXL2) , steroidogenic factor-1 (SF1) , anti-Müllerian hormone (AMH), HINTZ, HINTW , SRY HMG-box related gene 9 (SOX9) , and doublesex and mab-3 related transcription factor 1 (DMRT1) , have been shown to play important roles in the gonadal differentiation of chicken embryos.…”