The effect of substrate stiffness on adult neural stem cell behavior

Adult stem cells reside in unique niches that provide vital cues for their survival, self-renewal and differentiation. In order to better understand the contribution of substrate stiffness to neural stem/progenitor cell (NSPC) differentiation and proliferation, a photopolymerizable methacrylamide chitosan (MAC) biomaterial was developed. Photopolymerizable MAC is particularly compelling for the study of the central nervous system stem cell niche because Young's elastic modulus (E_Y) can be tuned from less than 1 kPa to greater than 30 kPa. Additionally, the numerous free amine functional groups enable inclusion of biochemical signaling molecules that, together with the mechanical environment, influence cell behavior. Herein, NSPCs proliferated on MAC substrates with Young's elastic moduli below 10 kPa and exhibited maximal proliferation on 3.5 kPa surfaces. Neuronal differentiation was favored on the softest surfaces with E_Y < 1 kPa as confirmed by both immunohistochemistry and qRT-PCR. Oligodendrocyte differentiation was favored on stiffer scaffolds (>7 kPa); however, myelin oligodendrocyte glycoprotein (MOG) gene expression suggested that oligodendrocyte maturation and myelination was best on <1 kPa scaffolds where more mature neurons were present. Astrocyte differentiation was only observed on <1 and 3.5 kPa surfaces and represented less than 2% of the total cell population. This work demonstrates the importance of substrate stiffness to the proliferation and differentiation of adult NSPCs and highlights the importance of mechanical properties to the success of scaffolds designed to engineer central nervous system tissue.     

Ontogeny and Microanatomy of the Nasal Turbinals in Lemuriformes

The nasal cavity of strepsirrhine primates (lemurs and lorises) has the most primitive arrangement of extant primates. In nocturnal species, the numerous turbinals of the ethmoid bear a large surface area of olfactory mucosa (OM). In this study, we examine turbinal development in four genera of diurnal or cathemeral lemuriformes. In addition, we examined an age series of each genus to detect whether structures bearing OM as opposed to respiratory mucosa (RM) develop differently, as has been observed in nocturnal strepsirrhines. In adults, the maxilloturbinal is covered by highly vascular respiratory mucosa throughout its entire length, with large sinusoidal vessels in the lamina propria; any parts of other turbinals that closely borders the maxilloturbinal has a similar mucosa. Posteriorly, the most vascular RM is restricted in the nasopharyngeal duct, which becomes partitioned from the dorsal olfactory region. A comparison of newborns to adults reveals that the first ethmoturbinal increases more in length in the parts that are covered with RM than OM, which supports the idea that ethmoturbinals can specialize in more than one function. Finally, we observe that the regions of turbinals that are ultimately covered with RM develop more accessory lamellae or additional surface area of existing scrolls compared to the regions covered with OM. Because such outgrowths of bone develop postnatally and without cartilaginous precursors, we hypothesize that the complexity of olfactory lamellae within the ethmoturbinal complex is primarily established at birth, while respiratory lamellae become elaborated due to the epigenetic influence of respiratory physiology. Anat Rec, 299:1492–1510, 2016. © 2016 Wiley Periodicals, Inc.     

Epigenome‐wide DNA methylation changes with development of arsenic‐induced skin lesions in Bangladesh: A case–control follow‐up study

Studies have found an association between aberrant DNA methylation and arsenic‐induced skin lesions. However, little is known about DNA methylation changes over time in people who develop arsenic‐induced skin lesions. We sought to investigate epigenome‐wide changes of DNA methylation in people who developed arsenic‐induced skin lesions in a 10‐year period. In 2009–2011, we conducted a follow‐up study of 900 skin lesion cases and 900 controls and identified 10 people who developed skin lesions since a baseline survey in 2001–2003. The 10 cases (“New Cases”) were matched with 10 controls who did not have skin lesions at baseline or follow‐up (“Persistent Controls”). Drinking water and blood samples were collected, and skin lesion was diagnosed by the same physician at both time points. We measured DNA methylation in blood using Infinium HumanMethylation450K BeadChip, followed by quantitative validation using pyrosequencing. Two‐sample t‐tests were used to compare changes in percent methylation between New Cases and Persistent Controls. Six CpG (cytosine‐phosphate‐guanine) sites with greatest changes of DNA methylation over time among New Cases were further validated with a correlation of 93% using pyrosequencing. One of the validated CpG site (cg03333116; change of %methylation was 13.2 in New Cases versus ?0.09 in Persistent Controls; P < 0.001) belonged to the RHBDF1 gene, which was previously reported to be hypermethylated in arsenic‐exposed cases. We examined DNA methylation changes with the development of arsenic‐induced skin lesions over time but nothing was statistically significant given the small sample size of this exploratory study and the high dimensionality of data. Environ. Mol. Mutagen. 55:449–456, 2014. © 2014 Wiley Periodicals, Inc.     

Biallelic loss of function variants in SYT2 cause a treatable congenital onset presynaptic myasthenic syndrome

Synaptotagmins are integral synaptic vesicle membrane proteins that function as calcium sensors and regulate neurotransmitter release at the presynaptic nerve terminal. Synaptotagmin‐2 (SYT2), is the major isoform expressed at the neuromuscular junction. Recently, dominant missense variants in SYT2 have been reported as a rare cause of distal motor neuropathy and myasthenic syndrome, manifesting with stable or slowly progressive distal weakness of variable severity along with presynaptic NMJ impairment. These variants are thought to have a dominant‐negative effect on synaptic vesicle exocytosis, although the precise pathomechanism remains to be elucidated. Here we report seven patients of five families, with biallelic loss of function variants in SYT2, clinically manifesting with a remarkably consistent phenotype of severe congenital onset hypotonia and weakness, with variable degrees of respiratory involvement. Electrodiagnostic findings were consistent with a presynaptic congenital myasthenic syndrome (CMS) in some. Treatment with an acetylcholinesterase inhibitor pursued in three patients showed clinical improvement with increased strength and function. This series further establishes SYT2 as a CMS‐disease gene and expands its clinical and genetic spectrum to include recessive loss‐of‐function variants, manifesting as a severe congenital onset presynaptic CMS with potential treatment implications.