Impacts of Fsh, Igf1, and high temperature on the expression of genes involved in steroidogenesis, cell communication, and apoptosis in isolated coho salmon previtellogenic ovarian follicles

From gametogenesis to spawning: How climate‐driven warming affects teleost reproductive biology

“…Beginning near the top of the BPG axis, a dampening of the Gnrh/Fsh system could contribute to reproductive dysfunction, as the ovary may suffer from a lack of stimulation to produce E2 (Elisio et al ., 2012). In addition, this problem would theoretically be exacerbated by reduced ovarian Fsh receptor ( fshr ) expression, a temperature‐induced feature of some teleost species (Anderson et al ., 2019; Elisio et al ., 2012). On the other hand, exposure to elevated temperature did not significantly impact fshr in S. salar during peak‐vitellogenesis (Anderson et al ., 2017a), and in this species E2 levels are severely reduced at high temperatures despite high levels of circulating Fsh (Anderson, Swanson, et al ., 2012).…”

“…Undoubtedly the best‐studied steroidogenic enzyme is Cyp19a1a, expression of which appears to be thermally sensitive in all adult fish species studied thus far (Table 3) (Anderson et al ., 2019; Anderson, Swanson, et al ., 2012; Elisio et al ., 2012; Mazzeo et al ., 2014). Studies on teleosts have strongly implicated forkhead transcription factor L2 ( foxl2 ) in the down‐regulation of Cyp19a1a since it is thermally sensitive during sex differentiation, and plays a role in Cyp19a1a (and 17α‐hydroxylase/C17,20‐lyase, Cyp17a1 ) transcription (Wang et al ., 2007; Yamaguchi et al ., 2007; Zhou et al ., 2007).…”

“…For example, the transport of cholesterol by the steroidogenic acute regulatory protein (Star) across the inner mitochondrial membrane is a crucial step in ovarian steroidogenesis (Lubzens et al ., 2010), yet expression of this gene does not appear to be thermally sensitive during early or peak‐vitellogenesis in S. salar (Anderson et al ., 2017a). In addition, expression of 3β‐hydroxysteroid dehydrogenase ( 3β‐hsd ) appears to be similarly uncompromised at high temperature during early vitellogenesis in coho salmon [ Oncorhynchus kisutch (Walbaum 1792)] in vitro (Anderson et al ., 2019), and during mid‐vitellogenesis in S. salar (Anderson et al ., 2017a). In contrast, Cyp11a1 (p450 cholesterol side‐chain cleavage protein) is strongly depressed during the later stages of vitellogenesis in S. salar (Anderson, Swanson, et al ., 2012), and Cyp17a1 is depressed by high temperature in O. kisutch primary growth follicles in vitro (Anderson et al ., 2019).…”

“…In addition, expression of 3β‐hydroxysteroid dehydrogenase ( 3β‐hsd ) appears to be similarly uncompromised at high temperature during early vitellogenesis in coho salmon [ Oncorhynchus kisutch (Walbaum 1792)] in vitro (Anderson et al ., 2019), and during mid‐vitellogenesis in S. salar (Anderson et al ., 2017a). In contrast, Cyp11a1 (p450 cholesterol side‐chain cleavage protein) is strongly depressed during the later stages of vitellogenesis in S. salar (Anderson, Swanson, et al ., 2012), and Cyp17a1 is depressed by high temperature in O. kisutch primary growth follicles in vitro (Anderson et al ., 2019). The molecular basis for reduced Cyp11a1 and Cyp17a1 is currently unclear.…”

From gametogenesis to spawning: How climate‐driven warming affects teleost reproductive biology

“…Beginning near the top of the BPG axis, a dampening of the Gnrh/Fsh system could contribute to reproductive dysfunction, as the ovary may suffer from a lack of stimulation to produce E2 (Elisio et al, 2012). In addition, this problem would theoretically be exacerbated by reduced ovarian Fsh receptor (fshr) expression, a temperature-induced feature of some teleost species (Anderson et al, 2019;Elisio et al, 2012). On the other hand, exposure to elevated temperature did not significantly impact fshr in S. salar during peak-vitellogenesis (Anderson et al, 2017a), and in this species E2 levels are severely reduced at high temperatures despite high levels of circulating Fsh (Anderson, Swanson, et al, 2012).…”