Brief exposure to warm temperatures reduces intron retention in Kdm6b in a species with temperature-dependent sex determination

Abstract

Animals with temperature-dependent sex determination (TSD) respond to thermal cues during early embryonic development to trigger gonadal differentiation. TSD has primarily been studied using constant temperature incubations, where embryos are exposed to constant male- or female-producing temperatures, and these studies have identified genes that display sex-specific expression in response to incubation temperature. Kdm6b , a histone demethylase gene, has received specific attention as it is among the initial genes to respond to incubation temperature and is necessary for testis development. Interestingly, Kdm6b retains an intron when eggs are incubated at a constant male-producing temperature, but the role of thermal variability in this developmental process is relatively understudied. Species with TSD regularly experience thermal cues that fluctuate between male- and female-producing temperatures throughout development but it is unclear how Kdm6b responds to such variable temperatures. In this study, we investigate temperature-sensitive splicing in Kdm6b by exposing embryos to male- and female-producing thermal conditions. We show a rapid decrease in levels of the intron retaining transcript of Kdm6b upon exposure to female-producing conditions. These results demonstrate that, under ecologically relevant conditions, temperature-sensitive splicing can differentially regulate genes critical to TSD.

Gene expression of male pathway genes sox9 and amh during early sex differentiation in a reptile departs from the classical amniote model

“…Histone modifiers jarid2 (Jumonji And AT-Rich Interaction Domain Containing 2) and kdm6b (Lysine Demethylase 6B) play a role in high temperature induced sex reversal in P. vitticeps [ 19 , 38 ] and in other evolutionary disparate TSD species [ 16 , 17 , 20 , 39 – 41 ]. Epigenetic regulation is also implicated in GSD sytems, for example in mice, where a Jumonji family member, Jmjd1a (Lysine Demethylase 3A), directly regulates expression of the sex determining gene Sry [ 42 ].…”

Truncated jarid2 and kdm6b transcripts are associated with temperature-induced sex reversal during development in a dragon lizard

“…The findings from this research open up many new avenues for future research, including determining the range of temperatures at which the ΔN variants may be functioning in P. vitticeps and demonstrating their function in regulating sex determination cascades. The effect temperature fluctuations during incubation in natural nests on splicing modulation also needed to be investigated ( 35 ).…”

“…Temperature-dependent alternative splicing is commonly observed in TSD reptiles and has been suggested to be an essential process in both TSD (24)(25)(26)(27)(28)(29) and sex reversal (30,31). For example, genes kdm6b and jarid2 and their differential splicing patterns have been implicated in the regulation of TSD in two species, the American alligator (Alligator mississippiensis) and the redeared slider turtle (Trachemys scripta) (32)(33)(34)(35)(36). Functional work in T. scripta has shown that KDM6B demethylates the promotor of a key sex gene dmrt1 (33) to determine the trajectory of the sex differentiation pathway (34,37).…”

How do maternal androgens and estrogens affect sex determination in reptiles with temperature‐dependent sex?

“…Studies carried out by Ge et al (2018) at constant temperatures showed that during TSP, the expression of kdm6b increases and that its repression leads to the development of female gonads, significantly increasing the expression of aromatase and foxl2 genes. In T. scripta, alternative splicing of kdm6b occurs due to temperature (Deveson et al, 2017) and has an important role in sex determination by temperature (Ge et al, 2018;Marroquín-Flores et al, 2021). At male-producing incubation temperatures, there is an increase in transcripts of kdm6b without introns.…”

“…At male‐producing incubation temperatures, there is an increase in transcripts of kdm6b without introns. However, when the eggs are incubated at fluctuating temperatures and the temperature increases, there is an increase in the amount of transcripts without introns, producing changes in the total expression of the protein (Marroquín‐Flores et al, 2021). The intron transcript would be responsible for increasing transcription rate of kdm6b , positively regulating drmt1 and generating male production in T. scripta .…”