Dietary Regimens Modify Early Onset of Obesity in Mice Haploinsufficient for Rai1

Smith-Magenis syndrome is a complex genomic disorder in which a majority of individuals are obese by adolescence. While an interstitial deletion of chromosome 17p11.2 is the leading cause, mutation or deletion of the RAI1 gene alone results in most features of the disorder. Previous studies have shown that heterozygous knockout of Rai1 results in an obese phenotype in mice and that Smith-Magenis syndrome mouse models have a significantly reduced fecundity and an altered transmission pattern of the mutant Rai1 allele, complicating large, extended studies in these models. In this study, we show that breeding C57Bl/6J Rai1+/−mice with FVB/NJ to create F1 Rai1+/− offspring in a mixed genetic background ameliorates both fecundity and Rai1 allele transmission phenotypes. These findings suggest that the mixed background provides a more robust platform for breeding and larger phenotypic studies. We also characterized the effect of dietary intake on Rai1+/− mouse growth during adolescent and early adulthood developmental stages. Animals fed a high carbohydrate or a high fat diet gained weight at a significantly faster rate than their wild type littermates. Both high fat and high carbohydrate fed Rai1+/− mice also had an increase in body fat and altered fat distribution patterns. Interestingly, Rai1+/− mice fed different diets did not display altered fasting blood glucose levels. These results suggest that dietary regimens are extremely important for individuals with Smith- Magenis syndrome and that food high in fat and carbohydrates may exacerbate obesity outcomes

De Novo ZMYND8 variants result in an autosomal dominant neurodevelopmental disorder with cardiac malformations

Purpose: ZMYND8 encodes a multidomain protein that serves as a central interactive hub for coordinating critical roles in transcription regulation, chromatin remodeling, regulation of superenhancers, DNA damage response and tumor suppression. We delineate a novel neurocognitive disorder caused by variants in the ZMYND8 gene. Methods: An international collaboration, exome sequencing, molecular modeling, yeast twohybrid assays, analysis of available transcriptomic data and a knockdown Drosophila model were used to characterize the ZMYND8 variants. Results: ZMYND8 variants were identified in 11 unrelated individuals; 10 occurred de novo and one suspected de novo; 2 were truncating, 9 were missense, of which one was recurrent. The disorder is characterized by intellectual disability with variable cardiovascular, ophthalmologic and minor skeletal anomalies. Missense variants in the PWWP domain of ZMYND8 abolish the interaction with Drebrin and missense variants in the MYND domain disrupt the interaction with GATAD2A. ZMYND8 is broadly expressed across cell types in all brain regions and shows highest expression in the early stages of brain development. Neuronal knockdown of the Drosophila ZMYND8 ortholog results in decreased habituation learning, consistent with a role in cognitive function. Conclusion: We present genomic and functional evidence for disruption of ZMYND8 as a novel etiology of syndromic intellectual disability

High carbohydrate and high fat fed <i>Rai1</i>^+/− mice have altered body fat and fat distribution.

<p>(<b>A</b>). Wild type and <i>Rai1^+/−</i> mice fed normal chow did not have significantly different total body fat. Both high carbohydrate and high fat fed <i>Rai1^+/−</i> mice had significantly more body fat than high carbohydrate and high fat fed wild type mice. (<b>B</b>). <i>Rai1</i>^+/− mice on a high fat diet had significantly more subcutaneous and abdominal fat relative to high fat fed wild type mice. However high carbohydrate fed <i>Rai1</i>^+/− mice only displayed alterations to abdominal fat portions but not subcutaneous. Normal chow diet regimen did not alter the distribution of fat in either genotype. All data are plotted as means +/− SEM; ** <i>P</i><0.01; *** <i>P</i><0.001; † <i>P</i><0.05; †† <i>P</i><0.01. NC: WT n = 3, <i>Rai1^+/−</i> n = 3. HC: WT n = 2, <i>Rai1^+/−</i> n = 4. HF WT n = 3, <i>Rai1^+/−</i> n = 3.</p

Blood glucose levels are not altered due to diet regimens.

<p>Mice fed either normal chow, high carbohydrate, or high fat do not have altered blood glucose levels after 12 hours of fasting. All data are plotted as mean +/− SEM. NC: WT n = 5, <i>Rai1^+/</i>⁻n = 8. HC: WT n = 3, <i>Rai1^+/−</i> n = 7. HF: WT n = 3, <i>Rai1^+/−</i> n = 5.</p

<i>Rai1^+/−</i> mice have improved fecundity in a FVB/NJ genetic background.

<p>(<b>A</b>). <i>Rai1^+/−</i> mice in the C57Bl/6J background when mated to C57Bl/6J produced significantly fewer progeny relative to <i>Rai1^+/−</i> mice mated to a FVB/NJ genetic background. In either background, the proportion of male and female progeny was not significantly different. No significant difference was observed for transmission of the <i>Rai1^+/−</i> allele by either parent (data not shown). (<b>B</b>). The number of <i>Rai1^+/−</i> progeny produced in a C57Bl/6J genetic background is significantly less than the number of wild type progeny produced, indicating altered Mendelian ratios; however, the number of <i>Rai1^+/−</i> progeny produced when mating occurs in the FVB/NJ genetic background is not significantly different than the number of wild type progeny, consistent with Mendelian transmission. Number of litters: C57Bl/6J x C57Bl/6J n = 19; C57Bl/6J x FVB/NJ n = 8, with either parent carrying the <i>Rai1^+/−</i> allele. (<b>C</b>). C57Bl/6J:FVB/NJ mixed background mice that are heterozygous at the <i>Rai1</i> locus have significantly reduced <i>Rai1</i> expression. All data are plotted as mean +/− SEM; n.s. = not significant; **<i>P</i><0.01; ***<i>P</i><0.001; ****<i>P</i><0.0001, WT n = 8, <i>Rai1^+/−</i> n = 8.</p

<i>Rai1</i>^+/− breeding in the C57Bl/6J genetic background.

<p><i>Rai1</i>^+/− breeding in the C57Bl/6J genetic background.</p

High carbohydrate and high fat diets alter growth rates in <i>Rai1</i>^+/− mixed background mice.

<p>(<b>A</b>). All mice fed a normal chow diet had similar growth rates during adolescence (weeks 5–9) or adulthood (weeks 10–16). No significant difference was observed in the amount of weight gained during each developmental stage. (<b>B</b>). <i>Rai1^+/−</i> mice fed a high carbohydrate diet had significantly faster growth during adolescence and adulthood relative to wild type mice. <i>Rai1^+/−</i> mice gained significantly more weight during adolescence and adulthood relative to wild type. (<b>C</b>). <i>Rai1^+/−</i> mice grew significantly faster and gained more weight when fed a high fat diet during both adolescent and adult stages of development relative to wild type mice. All data are plotted as means +/− SEM; dashed line represents the separation between developmental stages. Left panel; adolescence (weeks 5–9); n.s. = not significant; *<i>P</i><0.05; **<i>P</i><0.01; adulthood (weeks 10–16); n.s. = not significant; † <i>P</i><0.05; †† <i>P</i><0.01. Right panel; * <i>P</i><0.05. NC: WT n = 4, <i>Rai1^+/−</i> n = 8. HC: WT n = 3, <i>Rai1^+/−</i> n = 7. HF: WT n = 4, <i>Rai1^+/−</i> n = 3.</p