Novel homozygous LAMB1 in-frame deletion in a pediatric patient with brain anomalies and cerebrovascular event.

Biallelic pathogenic variants in LAMB1 have been associated with autosomal recessive lissencephaly 5 (OMIM 615191), which is characterized by brain malformations (cobblestone lissencephaly, hydrocephalus), developmental delay, and epilepsy. Pathogenic variants in LAMB1 are rare, with only 11 pathogenic variants and 11 patients reported to date. Here, we report on a 6-year-old patient from a consanguineous family with profound developmental delay, microcephaly, and a history of a perinatal cerebrovascular event. Brain magnetic resonance imaging (MRI) showed cerebellar cystic defects, signal intensity abnormalities, and a hypoplastic corpus callosum. Trio-exome analysis revealed a homozygous in-frame deletion of Exons 23 and 24 of LAMB1 affecting 104 amino acids including the epidermal growth factor (EGF)-like units 11 and 12 in Domain III. To our knowledge, this is the first reported in-frame deletion in LAMB1. Our findings broaden the clinical and molecular spectrum of LAMB1-associated syndromes.

Hes3 is expressed in the adult pancreatic islet and regulates gene expression, cell growth, and insulin release.

The transcription factor Hes3 is a component of a signaling pathway that supports the growth of neural stem cells with profound consequences in neurodegenerative disease models. Here we explored whether Hes3 also regulates pancreatic islet cells. We showed that Hes3 is expressed in human and rodent pancreatic islets. In mouse islets it co-localizes with alpha and beta cell markers. We employed the mouse insulinoma cell line MIN6 to perform in vitro characterization and functional studies in conditions known to modulate Hes3 based upon our previous work using neural stem cell cultures. In these conditions, cells showed elevated Hes3 expression and nuclear localization, grew efficiently, and showed higher evoked insulin release responses, compared with serum-containing conditions. They also exhibited higher expression of the transcription factor Pdx1 and insulin. Furthermore, they were responsive to pharmacological treatments with the GLP-1 analog Exendin-4, which increased nuclear Hes3 localization. We employed a transfection approach to address specific functions of Hes3. Hes3 RNA interference opposed cell growth and affected gene expression as revealed by DNA microarrays. Western blotting and PCR approaches specifically showed that Hes3 RNA interference opposes the expression of Pdx1 and insulin. Hes3 overexpression (using a Hes3-GFP fusion construct) confirmed a role of Hes3 in regulating Pdx1 expression. Hes3 RNA interference reduced evoked insulin release. Mice lacking Hes3 exhibited increased islet damage by streptozotocin. These data suggest roles of Hes3 in pancreatic islet function.

Streptozotocin-induced ß-cell damage, high fat diet, and metformin administration regulate Hes3 expression in the adult mouse brain.

Diabetes mellitus is a group of disorders characterized by prolonged high levels of circulating blood glucose. Type 1 diabetes is caused by decreased insulin production in the pancreas whereas type 2 diabetes may develop due to obesity and lack of exercise; it begins with insulin resistance whereby cells fail to respond properly to insulin and it may also progress to decreased insulin levels. The brain is an important target for insulin, and there is great interest in understanding how diabetes affects the brain. In addition to the direct effects of insulin on the brain, diabetes may also impact the brain through modulation of the inflammatory system. Here we investigate how perturbation of circulating insulin levels affects the expression of Hes3, a transcription factor expressed in neural stem and progenitor cells that is involved in tissue regeneration. Our data show that streptozotocin-induced ß-cell damage, high fat diet, as well as metformin, a common type 2 diabetes medication, regulate Hes3 levels in the brain. This work suggests that Hes3 is a valuable biomarker helping to monitor the state of endogenous neural stem and progenitor cells in the context of diabetes mellitus.

Hes3 expression in the adult mouse brain is regulated during demyelination and remyelination.

Hes3 is a component of the STAT3-Ser/Hes3 Signaling Axis controlling the growth and survival of neural stem cells and other plastic cells. Pharmacological activation of this pathway promotes neuronal rescue and behavioral recovery in models of ischemic stroke and Parkinson's disease. Here we provide initial observations implicating Hes3 in the cuprizone model of demyelination and remyelination. We focus on the subpial motor cortex of mice because we detected high Hes3 expression. This area is of interest as it is impacted both in human demyelinating diseases and in the cuprizone model. We report that Hes3 expression is reduced at peak demyelination and is partially restored within 1 week after cuprizone withdrawal. This raises the possibility of Hes3 involvement in demyelination/remyelination that may warrant additional research. Supporting a possible role of Hes3 in the maintenance of oligodendrocyte markers, a Hes3 null mouse strain shows lower levels of myelin basic protein in undamaged adult mice, compared to wild-type controls. We also present a novel method for culturing the established oligodendrocyte progenitor cell line oli-neu in a manner that maintains Hes3 expression as well as its self-renewal and differentiation potential, offering an experimental tool to study Hes3. Based upon this approach, we identify a Janus kinase inhibitor and dbcAMP as powerful inducers of Hes3 gene expression. We provide a new biomarker and cell culture method that may be of interest in demyelination/remyelination research.