Laboratorio de Herpetología, Facultad de Ciencias, Universidad Autónoma del Estado de México, Instituto Literario # 100 Centro, Toluca, Estado de México, México.
Laboratorio de Biología Tisular y Reproductora, Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad de México, México.
PLoS One. 2022 Jul 7;17(7):e0263804. doi: 10.1371/journal.pone.0263804. eCollection 2022.
Non-avian reptiles, unlike mammals and birds, have undergone numerous sex determination changes. Casque-Headed Lizards have replaced the ancestral XY system shared across pleurodonts with a new pair of XY chromosomes. However, the evolutionary forces that triggered this transition have remained unclear. An interesting hypothesis suggests that species with intermediate states, with sex chromosomes but also thermal-induced sex reversal at specific incubation temperatures, could be more susceptible to sex determination turnovers. We contrasted genotypic data (presence/absence of the Y chromosome) against the histology of gonads of embryos from stages 35-37 incubated at various temperatures, including typical male-producing (26°C) and female-producing (32°C) temperatures. Our work apparently reports for the first time the histology of gonads, including morphological changes, from stages 35-37 of development in the family Corytophanidae. We also observed that all embryos developed hemipenes, suggesting sex-linked developmental heterochrony. We observed perfect concordance between genotype and phenotype at all temperatures. However, analysis of transcriptomic data from embryos incubated at 26°C and 32°C identified transcript variants of the chromatin modifiers JARID2 and KDM6B that have been linked to temperature-dependent sex determination in other reptiles. Our work tested the validity of a mixed sex determination system in the family Corytophanidae. We found that XY chromosomes are dominant; however, our work supports the hypothesis of a conserved transcriptional response to incubation temperatures across non-avian reptiles that could be a reminiscence of an ancestral sex determination system.
非鸟类爬行动物与哺乳动物和鸟类不同，经历了多次性别决定变化。盔头蜥已经用一对新的 XY 染色体取代了 across pleurodonts 共享的祖先 XY 系统。然而，引发这种转变的进化力量仍不清楚。一个有趣的假设表明，具有中间状态的物种，即具有性染色体，但在特定孵化温度下也会发生热诱导性别反转，可能更容易发生性别决定翻转。我们将基因型数据（存在/不存在 Y 染色体）与在不同温度下孵化的 35-37 期胚胎性腺的组织学进行了对比，包括典型的雄性产生（26°C）和雌性产生（32°C）温度。我们的工作显然首次报告了科氏龙科发育阶段 35-37 期性腺的组织学，包括形态变化。我们还观察到所有胚胎都发育了半阴茎，表明与性别相关的发育异时性。我们在所有温度下都观察到基因型和表型之间的完美一致性。然而，对在 26°C 和 32°C 下孵化的胚胎的转录组数据进行分析，鉴定出了与其他爬行动物中温度依赖性性别决定相关的染色质修饰剂 JARID2 和 KDM6B 的转录变体。我们的工作检验了科氏龙科混合性别决定系统的有效性。我们发现 XY 染色体占主导地位；然而，我们的工作支持了一个保守的转录反应假说，即在非鸟类爬行动物中，对孵化温度的反应可能是对祖先性别决定系统的回忆。
