Modeling human epilepsy by TALEN targeting of mouse sodium channel Scn8a

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106152/1/dvg22731.pd

The SCN8A encephalopathy mutation p.Ile1327Val displays elevated sensitivity to the anticonvulsant phenytoin

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134291/1/epi13461_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134291/2/epi13461.pd

Correlated evolution of androgen receptor and aromatase revisited

Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Molecular Biology and Evolution 27 (2010): 2211-2215, doi:10.1093/molbev/msq129.Conserved interactions among proteins or other molecules can provide strong evidence for coevolution across their evolutionary history. Diverse phylogenetic methods have been applied to identify potential coevolutionary relationships. In most cases, these methods minimally require comparisons of orthologous sequences and appropriate controls to separate effects of selection from the overall evolutionary relationships. In vertebrates, androgen receptor (AR) and cytochrome p450 aromatase (CYP19) share an affinity for androgenic steroids, which serve as receptor ligands and enzyme substrates. In a recent study, Tiwary and Li (2009) reported that AR and CYP19 displayed a signature of ancient and conserved interactions throughout all of the Eumetazoa (i.e., cnidarians, protostomes, and deuterostomes). Because these findings conflicted with a number of previous studies, we reanalyzed the data set used by Tiwary and Li. First, our analyses demonstrate that the invertebrate genes used in the previous analysis are not orthologous sequences, but instead represent a diverse set of nuclear receptors and cytochrome p450 enzymes with no confirmed or hypothesized relationships with androgens. Second, we show that (1) their analytical approach, which measures correlations in evolutionary distances between proteins, potentially led to spurious significant relationships due simply to conserved domains and (2) control comparisons provide positive evidence for a strong influence of evolutionary history. We discuss how corrections to this method and analysis of key taxa (e.g., duplications in the teleost fish and suiform lineages) can inform investigations of the coevolutionary relationships between androgen receptor and aromatase.AMR was supported by the Postdoctoral Scholar Program at the Woods Hole Oceanographic Institution, with funding provided by The Beacon Institute for Rivers and Estuaries, and AMT was supported by WHOI Assistant Scientist Endowed Support

A null mutation of the neuronal sodium channel NaV1.6 disrupts action potential propagation and excitation‐contraction coupling in the mouse heart

Evidence supports the expression of brain‐type sodium channels in the heart. Their functional role, however, remains controversial. We used global NaV1.6‐null mice to test the hypothesis that NaV1.6 contributes to the maintenance of propagation in the myocardium and to excitation‐contraction (EC) coupling. We demonstrated expression of transcripts encoding full‐length NaV1.6 in isolated ventricular myocytes and confirmed the striated pattern of NaV1.6 fluorescence in myocytes. On the ECG, the PR and QRS intervals were prolonged in the null mice, and the Ca2+ transients were longer in the null cells. Under patch clamping, at holding potential (HP) = –120 mV, the peak INa was similar in both phenotypes. However, at HP = –70 mV, the peak INa was smaller in the nulls. In optical mapping, at 4 mM [K+]o, 17 null hearts showed slight (7%) reduction of ventricular conduction velocity (CV) compared to 16 wild‐type hearts. At 12 mM [K+]o, CV was 25% slower in a subset of 9 null vs. 9 wild‐type hearts. These results highlight the importance of neuronal sodium channels in the heart, whereby NaV1.6 participates in EC coupling, and represents an intrinsic depolarizing reserve that contributes to excitation.—Noujaim, S. F., Kaur, K., Milstein, M., Jones, J. M., Furspan, P., Jiang, D., Auerbach, D. S., Herron, T., Meisler, M. H., Jalife, J. A null mutation of the neuronal sodium channel NaV1.6 disrupts action potential propagation and excitation‐contraction coupling in the mouse heart. FASEB J. 26, 63–72 (2012). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154524/1/fsb2fj10179770.pd

C9 ORF 72 expansion in a family with bipolar disorder

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98405/1/bdi12063.pd

Murine Fig4 is dispensable for muscle development but required for muscle function

Abstract Background Phosphatidylinositol phosphates (PIPs) are low-abundance phospholipids that participate in a range of cellular processes, including cell migration and membrane traffic. PIP levels and subcellular distribution are regulated by a series of lipid kinases and phosphatases. In skeletal muscle, PIPs and their enzymatic regulators serve critically important functions exemplified by mutations of the PIP phosphatase MTM1 in myotubular myopathy (MTM), a severe muscle disease characterized by impaired muscle structure and abnormal excitation–contraction coupling. FIG4 functions as a PIP phosphatase that participates in both the synthesis and breakdown of phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2). Mutation of FIG4 results in a severe neurodegenerative disorder in mice and a progressive peripheral polyneuropathy in humans. The effect of FIG4 mutation on skeletal muscle has yet to be examined. Methods Herein we characterize the impact of FIG4 on skeletal muscle development and function using the spontaneously occurring mouse mutant pale tremor (plt), a mouse line with a loss of function mutation in Fig4. Results In plt mice, we characterized abnormalities in skeletal muscle, including reduced muscle size and specific force generation. We also uncovered ultrastructural abnormalities and increased programmed cell death. Conversely, we detected no structural or functional abnormalities to suggest impairment of excitation–contraction coupling, a process previously shown to be influenced by PI(3,5)P2 levels. Conditional rescue of Fig4 mutation in neurons prevented overt muscle weakness and the development of obvious muscle abnormalities, suggesting that the changes observed in the plt mice were primarily related to denervation of skeletal muscle. On the basis of the ability of reduced FIG4 levels to rescue aspects of Mtmr2-dependent neuropathy, we evaluated the effect of Fig4 haploinsufficiency on the myopathy of Mtm1-knockout mice. Male mice with a compound Fig4 +/−/Mtm1 –/Y genotype displayed no improvements in muscle histology, muscle size or overall survival, indicating that FIG4 reduction does not ameliorate the Mtm1-knockout phenotype. Conclusions Overall, these data indicate that loss of Fig4 impairs skeletal muscle function but does not significantly affect its structural development.http://deepblue.lib.umich.edu/bitstream/2027.42/112676/1/13395_2013_Article_83.pd

Characterization of a de novo SCN8A mutation in a patient with epileptic encephalopathy

Objective Recently, de novo SCN8A missense mutations have been identified as a rare dominant cause of epileptic encephalopathies. Functional studies on the first described case demonstrated gain-of-function effects of the mutation. We describe a novel de novo mutation of SCN8A in a patient with epileptic encephalopathy, and functional characterization of the mutant protein. Design Whole exome sequencing was used to discover the variant. We generated a mutant cDNA, transfected HEK293 cells, and performed Western blotting to assess protein stability. To study channel functional properties, patch-clamp experiments were carried out in transfected neuronal ND7/23 cells. Results The proband exhibited seizure onset at 6 months of age, diffuse brain atrophy, and more profound developmental impairment than the original case. The mutation p.Arg233Gly in the voltage sensing transmembrane segment D1S4 was present in the proband and absent in both parents. This mutation results in a temperature-sensitive reduction in protein expression as well as reduced sodium current amplitude and density and a relative increased response to a slow ramp stimulus, though this did not result in an absolute increased current at physiological temperatures. Conclusion The new de novo SCN8A mutation is clearly deleterious, resulting in an unstable protein with reduced channel activity. This differs from the gain-of-function attributes of the first SCN8A mutation in epileptic encephalopathy, pointing to heterogeneity of mechanisms. Since Nav1.6 is expressed in both excitatory and inhibitory neurons, a differential effect of a loss-of-function of Nav1.6 Arg223Gly on inhibitory interneurons may underlie the epilepsy phenotype in this patient

Localization of insulin-2 (Ins-2) and the obesity mutant tubby (tub) to distinct regions of mouse chromosome 7

A DNA mapping panel derived from an interspecific backcross was used to position the mouse insulin-2 locus (Ins-2) on Chromosome 7, near H19 (0/114 recombinants) and Th (1/114 recombinants). Ins-2 is part of a human-mouse conserved linkage group that includes Th, H19, and Igf-2. Analysis of segregation in the F2 generation from the cross C57BL/6J-tub/tub x CAST/Ei demonstrated that Ins-2 and the obesity mutant tubby (tub) are distinct loci, thus eliminating Ins-2 as a candidate gene for tub. These results also refine the estimated genetic distance between tub and Hbb to 2.4 [plus-or-minus sign] 1.4 cM. The predicted location for a human homolog of tubby is HSA 11p15.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29864/1/0000212.pd

Neurocognitive mechanisms of co‐occurring math difficulties in dyslexia: Differences in executive function and visuospatial processing

Children with dyslexia frequently also struggle with math. However, studies of reading disability (RD) rarely assess math skill, and the neurocognitive mechanisms underlying co-occurring reading and math disability (RD+MD) are not clear. The current study aimed to identify behavioral and neurocognitive factors associated with co-occurring MD among 86 children with RD. Within this sample, 43% had co-occurring RD+MD and 22% demonstrated a possible vulnerability in math, while 35% had no math difficulties (RD-Only). We investigated whether RD-Only and RD+MD students differed behaviorally in their phonological awareness, reading skills, or executive functions, as well as in the brain mechanisms underlying word reading and visuospatial working memory using functional magnetic resonance imaging (fMRI). The RD+MD group did not differ from RD-Only on behavioral or brain measures of phonological awareness related to speech or print. However, the RD+MD group demonstrated significantly worse working memory and processing speed performance than the RD-Only group. The RD+MD group also exhibited reduced brain activations for visuospatial working memory relative to RD-Only. Exploratory brain-behavior correlations along a broad spectrum of math ability revealed that stronger math skills were associated with greater activation in bilateral visual cortex. These converging neuro-behavioral findings suggest that poor executive functions in general, including differences in visuospatial working memory, are specifically associated with co-occurring MD in the context of RD