Potential Contributions of Heat Shock Proteins to Temperature-Dependent Sex Determination in the American Alligator

Abstract

Sex determination in the American alligator depends on the incubation temperature experienced during a thermo-sensitive period (TSP), although sex determination can be ‘reversed’ by embryonic exposure to an estrogenic compound. Thus, temperature and estrogenic signals play essential roles during temperature-dependent sex determination (TSD). The genetic basis for TSD is poorly understood, although previous studies observed that many of the genes associated with genetic sex determination (GSD) are expressed in species with TSD. Heat shock proteins (HSPs), good candidates because of their temperature-sensitive expression, have not been examined in regard to TSD but HSPs have the ability to modify steroid receptor function. A number of HSP cDNAs (HSP27, DNAJ, HSP40, HSP47, HSP60, HSP70A, HSP70B, HSP70C, HSP75, HSP90α, HSP90β, and HSP108) as well as cold-inducible RNA binding protein (CIRBP) and HSP-binding protein (HSPBP) were cloned, and expression of their mRNA in the gonadal-adrenal-mesonephros complex (GAM) was investigated. Embryonic and neonatal GAMs exhibited mRNA for all of the HSPs examined during and after the TSP. One-month-old GAMs were separated into 3 portions (gonad, adrenal gland, and mesonephros), and sexual dimorphism in the mRNA expression of gonadal HSP27 (male > female), gonadal HSP70A (male < female), and adrenal HSP90α (male > female) was observed. These findings provide new insights on TSD and suggest that further studies examining the role of HSPs during gonadal development are needed.

Differential expression analysis of genes involved in high-temperature induced sex differentiation in Nile tilapia

“…Whether HSP90 expression increases after heat shock is used for associating with steroid hormone receptors remains unknown. Previous studies have shown that gonadal HSP27 can reduce the E2 signal directly at trans-activation, whereas gonadal HSP70A could induce E2 signaling by stimulating vitamin D signaling that leads to the induction of augmented CYP19A1 expression (Kohno et al, 2010). In this study, we found that the expressions of HSP27 and HSP70 were up-regulated after heat shock, whereas the role of increased expressions of HSP27 and HSP70 remains to be elucidated.…”

“…Heat shock proteins (HSPs) are a class of functionally related proteins involved in the folding and unfolding of other proteins and their expressions are induced by heat and other stresses (Kohno et al, 2010). It is reported that for several steroid receptors, binding to HSP90 was required for the receptor to be in a native hormonebinding state, and for all of the receptors, hormone binding promoted dissociation of the receptor from HSP90 and conversion of the receptor to the DNA-binding state (Pratt and Toft, 1997).…”

“…Furthermore, heat shock protein 27 as an estrogen receptor-β (ERβ) associated protein could act as a co-repressor of estrogen signaling (Al-Madhoun et al, 2007). As a result, HSPs are interesting candidates to play important roles during the interaction of temperature and estrogen signaling (Kohno et al, 2010).…”

Incubation history prior to the canonical thermosensitive period determines sex in the American alligator

“…Validation of this molecular sex assessment indicates that there is a 98.7% (213/216) concordance between histology-based sex assignment and that based on expression patterns of sexually dimorphic genes (Kohno et al 2015). RNA isolation, purification, and RT were conducted as previously reported (Kohno et al 2010). Expression levels were determined by comparison to plasmid DNA standard curves that contained known copies of each target gene amplicon.…”

Disorders of Sexual Development and Abnormal Early Development in Domestic Food-Producing Mammals: The Role of Chromosome Abnormalities, Environment and Stress Factors

“…The genetic basis for TSD is poorly understood, although previous studies observed that many of the genes associated with genetic sex determination (GSD) are expressed in species with TSD. HSP27, HSP70A and HSP90 ␣ are associated with an increase of 1 sex versus the other, with HSP27 and 90 ␣ favoring the male and HSP70A favoring females [Kohno et al, 2010]. It has been shown that egg incubation temperature influences sex ratio in some reptiles as the incubation temperature interferes with the aromatase activity, resulting in a sex-determination mechanism thought to be lost in mammals.…”