Cross_Domain_InhDis_Supplement – Supplemental material for Quantifying Inhibitory Control as Externalizing Proneness: A Cross-Domain Model

<p>Supplemental material, Cross_Domain_InhDis_Supplement for Quantifying Inhibitory Control as Externalizing Proneness: A Cross-Domain Model by Noah C. Venables, Jens Foell, James R. Yancey, Michael J. Kane, Randall W. Engle, and Christopher J. Patrick in Clinical Psychological Science</p

Mice Genetically Depleted of Brain Serotonin Display Social Impairments, Communication Deficits and Repetitive Behaviors: Possible Relevance to Autism

<div><p>Autism is a complex neurodevelopmental disorder characterized by impaired reciprocal social interaction, communication deficits and repetitive behaviors. A very large number of genes have been linked to autism, many of which encode proteins involved in the development and function of synaptic circuitry. However, the manner in which these mutated genes might participate, either individually or together, to cause autism is not understood. One factor known to exert extremely broad influence on brain development and network formation, and which has been linked to autism, is the neurotransmitter serotonin. Unfortunately, very little is known about how alterations in serotonin neuronal function might contribute to autism. To test the hypothesis that serotonin dysfunction can contribute to the core symptoms of autism, we analyzed mice lacking brain serotonin (via a null mutation in the gene for tryptophan hydroxylase 2 (TPH2)) for behaviors that are relevant to this disorder. Mice lacking brain serotonin (TPH2−/−) showed substantial deficits in numerous validated tests of social interaction and communication. These mice also display highly repetitive and compulsive behaviors. Newborn TPH2−/− mutant mice show delays in the expression of key developmental milestones and their diminished preference for maternal scents over the scent of an unrelated female is a forerunner of more severe socialization deficits that emerge in weanlings and persist into adulthood. Taken together, these results indicate that a hypo-serotonin condition can lead to behavioral traits that are highly characteristic of autism. Our findings should stimulate new studies that focus on determining how brain hyposerotonemia during critical neurodevelopmental periods can alter the maturation of synaptic circuits known to be mis-wired in autism and how prevention of such deficits might prevent this disorder.</p> </div

Mating success rates in TPH2+/+, TPH2+/- and TPH2-/- mice.

<p>Mating pairs of the indicated genotypes were caged together for 21 days after which the male was removed. From this time forward, the female was housed alone until pups were born or until the passage of an additional 21 days. Matings were scored as successful if pups were born and matings that extended beyond the 21 day post-mating period without births were deemed unsuccessful. Statistical comparisons among rows and the level of significance is indicated below: row 1 different from rows 4 (p < 0.0001), 5 (p = 0.015) and 6 (p < 0.0001); row 2 different from rows 4 (p < 0.0001), 5 (p = 0.008) and 6 (p < 0.0001); row 3 different from row 6 (p = 0.011); row 4 different from rows 1 (p < 0.0001), 2 (p < 0.0001), and 6 (p = 0.011); row 5, different from 1 (p = 0.015), 2 (p = 0.008), and 6 (p < 0.0001); and row 6, different from rows 1 (p < 0.0001), 2 (p < 0.0001), 3 (p = 0.011), 4 (p = 0.011), and 5 (p < 0.0001).</p><p>Mating success rates in TPH2+/+, TPH2+/- and TPH2-/- mice.</p

Social memory in weanling TPH2−/− mice.

<p>(A) latency to first investigate and (B) total time spent investigating the same stranger mouse on habituation trials 1–3 and a novel stranger on dishabituation trial 4. Data are presented as mean ± standard errors of the mean and are based on 12 TPH2−/− mice (6 males and 6 females) and 12 WT controls (6 males, 6 females). The main effect of sex was not significant so data for males and females is combined. Symbol indicates significant difference between WT and TPH2−/− (* p<0.025) or between habituation trial 3 and the dishabituation trial (# p<0.025).</p

Urine scent marking in adult male TPH2−/− mice.

<p>(A) latency to first investigate urine spot from an estrous female, (B) time spent investigating urine spot from an estrous female, (C) number of urine deposits over the entire cage and (D) number of urine deposits in the immediate vicinity of the urine spot from an estrous female. Data are presented as mean ± standard error of the mean and are based on 7 TPH2−/− mice and 8 WT mice. Symbols indicate significant differences from WT controls. * p<0.05; ** p<0.01.</p

Developmental milestones, brain weight and social recognition in pre-weanling TPH2−/− pups.

<p>(A) acquisition of somatosensory reflexes and developmental milestones from PND 1–19. The indicated reflexes and milestones were considered acquired when they occurred for the second day in a row. (B) brain to body weight ratios in PND 25–28 mice and (C) maternal scent recognition in PND 14 mice. Data in panels (A) and (C) was collected from 6 independent litters for each genotype. Data included in panel (B) was based on results from 18 TPH2−/− (7 male, 11 female) and 31 WT controls (16 male, 15 female). The main effect of sex was not significant so data for males and females is combined. Data are presented as mean ± standard errors of the mean. Symbols indicate significant differences versus WT controls. * p<0.05; ** p<0.01; *** p<0.001.</p

Male sexual preference when exposed to two mice simultaneously.

<p>(A) # of mounts by WT or KO males when exposed simultaneously to a WT male versus a WT female or to a WT male versus a KO female, (B) # of intromissions by WT and KO males when exposed simultaneously to two mice as described in A, (C) # of aggressive attacks by WT and KO males when exposed simultaneously to two mice as described in A, (D) # of mounts by WT or KO males when exposed simultaneously to a receptive WT female and a receptive KO female, (E) % investigation time when WT or KO males were exposed simultaneously to a “caged” WT male versus a “caged” WT female or to a “caged” WT male versus a “caged” KO female. Data are expressed as the mean ± SEM for groups containing 6–11 WT and 10 KO males. Symbols indicate significant difference from the WT control (female or male). * p < 0.05; ** p < 0.01; **** p < 0.0001.</p

Social olfactory discrimination in adult TPH2−/− mice.

<p>(A) % time spent sniffing litter scented by stranger mouse versus that from test subject's own cage and (B) total time spent sniffing. Data are presented as mean ± standard errors of the mean and are based on 22 TPH2−/− mice (10 males, 12 females) and 21 WT controls (10 males, 11 females). The main effect of sex was not significant so data for males and females is combined. Symbols indicate significant differences from WT controls. * p<0.05; *** p<0.001.</p

Novel object test of restricted interests in weanling TPH2−/− mice.

<p>(A) latency to first investigate, (B) total number of contacts and (C) total time investigating a novel object. Data are presented as mean ± standard errors of the mean and are based on 20 TPH2−/− mice (10 males, 10 females) and 22 WT controls (11 males, 11 females). The main effect of sex was not significant so data for males and females is combined. Symbols indicate significant differences from WT controls. ** p<0.01.</p

Social memory in TPH2−/− adult mice.

<p>(A) latency to first investigate and (B) total time spent investigating the same stranger mouse on habituation trials 1–3 and a novel stranger on dishabituation trial 4. Data are presented as mean ± standard errors of the mean and are based on 12 TPH2−/− mice (6 males and 6 females) and 12 WT controls (6 males, 6 females). The main effect of sex was not significant so data for males and females is combined. Symbols indicate significant difference between WT and TPH2−/− (* p<0.05, *** p<0.001) or between habituation trial 3 and the dishabituation trial (### p<0.001).</p