School Of Basic And Applied Sciences

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    Genome-wide association study of 25(OH) Vitamin D concentrations in Punjabi Sikhs: Results of the Asian Indian diabetic heart study
    (Elsevier Ltd, 2016) Sapkota, B.R.; Hopkins, R.; Bjonnes, A.; Ralhan, S.; Wander, G.S.; Mehra, N.K.; Singh, J.R.; Blackett, P.R.; Saxena, R.; Sanghera, D.K.
    Vitamin D deficiency is implicated in multiple disease conditions and accumulating evidence supports that the variation in serum vitamin D (25(OH)D) levels, including deficiency, is under strong genetic control. However, the underlying genetic mechanism associated with vitamin 25(OH)D concentrations is poorly understood. We earlier reported a very high prevalence of vitamin D deficiency associated with an increased risk for type 2 diabetes and obesity in a Punjabi Sikh diabetic cohort as part of the Asian Indian diabetic heart study (AIDHS). Here we have performed the first genome-wide association study (GWAS) of serum 25(OH)D on 3538 individuals from this Punjabi Sikh population. Our discovery GWAS comprised of 1387 subjects followed by validation of 24 putative SNPs (P < 10-4) using an independent replication sample (n = 2151) from the same population by direct genotyping. A novel locus at chromosome 20p11.21 represented by rs2207173 with minor allele frequency (MAF) 0.29, [? = -0.13, p = 4.47 ? 10-9] between FOXA2 and SSTR4 was identified to be associated with 25(OH)D levels. Another suggestive association signal at rs11586313 (MAF 0.54) [? = 0.90; p = 1.36 ? 10-6] was found within the regulatory region of the IVL gene on chromosome 1q21.3. Additionally, our study replicated 3 of 5 known GWAS genes associated with 25(OH)D concentrations including GC (p = 0.007) and CYP2R1 (p = 0.019) reported in Europeans and the DAB1 (p = 0.003), reported in Hispanics. Identification of novel association signals in biologically plausible regions with 25(OH)D metabolism will provide new molecular insights on genetic drivers of vitamin D status and its implications in health disparities. ? 2015 Elsevier Ltd. All rights reserved.
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    Stage-specific functions of Semaphorin7A during adult hippocampal neurogenesis rely on distinct receptors
    (Nature Publishing Group, 2017) Jongbloets, Bart C.; Lemstra, Suzanne; Schellino, Roberta; Broekhoven, Mark H.; Parkash, Jyoti; Hellemons, Anita J.C.G.M.; Mao, Tianyi; Giocobini, Paolo; Praag, Henriette Van; Marchis, Silvia De; Ramakers, Geert M.J.; Pasterkamp, R. Jeroen; Jongbloets, B.C.; Lemstra, S.; Schellino, R.; Broekhoven, M.H.; Parkash, J.; Hellemons, A.J.C.G.M.; Mao, T.; Giacobini, P.; Van Praag, H.; De Marchis, S.; Ramakers, G.M.J.; Pasterkamp, R.J.
    The guidance protein Semaphorin7A (Sema7A) is required for the proper development of the immune and nervous systems. Despite strong expression in the mature brain, the role of Sema7A in the adult remains poorly defined. Here we show that Sema7A utilizes different cell surface receptors to control the proliferation and differentiation of neural progenitors in the adult hippocampal dentate gyrus (DG), one of the select regions of the mature brain where neurogenesis occurs. PlexinC1 is selectively expressed in early neural progenitors in the adult mouse DG and mediates the inhibitory effects of Sema7A on progenitor proliferation. Subsequently, during differentiation of adult-born DG granule cells, Sema7A promotes dendrite growth, complexity and spine development through ?1-subunit-containing integrin receptors. Our data identify Sema7A as a key regulator of adult hippocampal neurogenesis, providing an example of how differential receptor usage spatiotemporally controls and diversifies the effects of guidance cues in the adult brain.