Transcriptomic alterations in the brain of painted turtles (Chrysemys picta) developmentally exposed to bisphenol A or ethinyl estradiol.

Developmental exposure of turtles and other reptiles to endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE), can stimulate partial to full gonadal sex-reversal in males. We have also recently shown that in ovo exposure to either EDC can induce similar sex-dependent behavioral changes typified by improved spatial learning and memory or possibly feminized brain responses. Observed behavioral changes are presumed to be due to BPA- and EE-induced brain transcriptomic alterations during development. To test this hypothesis, we treated painted turtles (Chrysemys picta) at developmental stage 17, incubated at 26°C (male-inducing temperature), with 1) BPA (1 ng/µl), 2) EE (4 ng/µl), or 3) vehicle ethanol (control group). Ten months after hatching and completion of the behavioral tests, juvenile turtles were euthanized, brains were collected and frozen in liquid nitrogen, and RNA was isolated for RNA-Seq analysis. Turtles exposed to BPA clustered separately from EE-exposed and control individuals. More transcripts and gene pathways were altered in BPA vs. EE individuals. The one transcript upregulated in both BPA- and EE-exposed individuals was the mitochondrial-associated gene, ND5, which is involved in oxidative phosphorylation. Early exposure of turtles to BPA increases transcripts linked with ribosomal and mitochondrial functions, especially bioenergetics, which has been previously linked with improved cognitive performance. In summary, even though both BPA and EE resulted in similar behavioral alterations, they diverge in the pattern of neural transcript alterations with early BPA significantly upregulating several genes involved in oxidative phosphorylation, mitochondrial activity, and ribosomal function, which could enhance cognitive performance.

Effects of developmental exposure to bisphenol A and ethinyl estradiol on spatial navigational learning and memory in painted turtles (Chrysemys picta).

Developmental exposure of turtles and other reptiles to endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE2, estrogen present in birth control pills), can induce partial to full gonadal sex-reversal in males. No prior studies have considered whether in ovo exposure to EDCs disrupts normal brain sexual differentiation. Yet, rodent model studies indicate early exposure to these chemicals disturbs sexually selected behavioral traits, including spatial navigational learning and memory. Thus, we sought to determine whether developmental exposure of painted turtles (Chrysemys picta) to BPA and EE2 results in sex-dependent behavioral changes. At developmental stage 17, turtles incubated at 26°C (male-inducing temperature) were treated with 1) BPA High (100µg /mL), 2) BPA Low (0.01µg/mL), 3) EE2 (0.2µg/mL), or 4) vehicle or no vehicle control groups. Five months after hatching, turtles were tested with a spatial navigational test that included four food containers, only one of which was baited with food. Each turtle was randomly assigned one container that did not change over the trial period. Each individual was tested for 14 consecutive days. Results show developmental exposure to BPA High and EE2 improved spatial navigational learning and memory, as evidenced by increased number of times spent in the correct target zone and greater likelihood of solving the maze compared to control turtles. This study is the first to show that in addition to overriding temperature sex determination (TSD) of the male gonad, these EDCs may induce sex-dependent behavioral changes in turtles.

Characterization of vocalizations emitted in isolation by California mouse (Peromyscus californicus) pups throughout the postnatal period.

Rodent species, such as monogamous and biparental California mice, produce vocalizations as a means of communication. A temporal examination of vocalizations produced by California mice pups in isolation was performed. Pup recordings were performed for 3 min at ∼10.00 and 14.00 hrs on early postnatal days (PND) 2-4, 7, 21, and 28. Once initial recordings were finished, pups were returned to the home cage with parents and any siblings for 5 minutes to determine if active biparental responses resulted in an enhanced vocalization response when pups were isolated and retested. We also sought to determine whether potential reduction in vocalizations by older pups might be due to procedure-habituation procedure associated with less anxiety and/or possibly decreased need for parental care. Vocalizations were measured in weanling (30 days of age) "naïve" pups not previously isolated. Results show older pups took significantly longer to vocalize, indicated by increased latency before producing their initial syllable compared to earlier ages. With increasing age, pups demonstrated decreased syllable duration, reduced number and duration of phrases, and decreased number of syllables per phrase. No differences in pup vocalizations were observed before and after being placed back with parents, suggestive biparental potentiation may not exist in California mice pups. Comparison of the naïve to habituated weanling pups indicated the former group had more total calls but no other differences in vocalization parameters were detected between these 2 groups. Collectively, the findings suggest that as California mice pups mature and approach weaning they generally vocalize less in isolation. (PsycINFO Database Record