Human ACE2 receptor polymorphisms and altered susceptibility to SARS-CoV-2.

COVID-19 is a respiratory illness caused by a novel coronavirus called SARS-CoV-2. The viral spike (S) protein engages the human angiotensin-converting enzyme 2 (ACE2) receptor to invade host cells with ~10-15-fold higher affinity compared to SARS-CoV S-protein, making it highly infectious. Here, we assessed if ACE2 polymorphisms can alter host susceptibility to SARS-CoV-2 by affecting this interaction. We analyzed over 290,000 samples representing >400 population groups from public genomic datasets and identified multiple ACE2 protein-altering variants. Using reported structural data, we identified natural ACE2 variants that could potentially affect virus-host interaction and thereby alter host susceptibility. These include variants S19P, I21V, E23K, K26R, T27A, N64K, T92I, Q102P and H378R that were predicted to increase susceptibility, while variants K31R, N33I, H34R, E35K, E37K, D38V, Y50F, N51S, M62V, K68E, F72V, Y83H, G326E, G352V, D355N, Q388L and D509Y were predicted to be protective variants that show decreased binding to S-protein. Using biochemical assays, we confirmed that K31R and E37K had decreased affinity, and K26R and T92I variants showed increased affinity for S-protein when compared to wildtype ACE2. Consistent with this, soluble ACE2 K26R and T92I were more effective in blocking entry of S-protein pseudotyped virus suggesting that ACE2 variants can modulate susceptibility to SARS-CoV-2.

Harnessing region-specific neurovascular signaling to promote germinal matrix vessel maturation and hemorrhage prevention.

Germinal matrix hemorrhage (GMH), affecting about 1 in 300 births, is a major perinatal disease with lifelong neurological consequences. Yet despite advances in neonatal medicine, there is no effective intervention. GMH is characterized by localized bleeding in the germinal matrix (GM), due to inherent vessel fragility unique to this developing brain region. Studies have shown that reduced TGFß signaling contributes to this vascular immaturity. We have previously shown that a region-specific G-protein-coupled receptor pathway in GM neural progenitor cells regulates integrin ß8, a limiting activator of pro-TGFß. In this study, we use mice to test whether this regional pathway can be harnessed for GMH intervention. We first examined the endogenous dynamics of this pathway and found that it displays specific patterns of activation. We then investigated the functional effects of altering these dynamics by chemogenetics and found that there is a narrow developmental window during which this pathway is amenable to manipulation. Although high-level activity in this time window interferes with vessel growth, moderate enhancement promotes vessel maturation without compromising growth. Furthermore, we found that enhancing the activity of this pathway in a mouse model rescues all GMH phenotypes. Altogether, these results demonstrate that enhancing neurovascular signaling through pharmacological targeting of this pathway may be a viable approach for tissue-specific GMH intervention. They also demonstrate that timing and level are likely two major factors crucial for success. These findings thus provide critical new insights into both brain neurovascular biology and the intervention of GMH.

A Brain-Region-Specific Neural Pathway Regulating Germinal Matrix Angiogenesis.

Intimate communication between neural and vascular cells is critical for normal brain development and function. Germinal matrix (GM), a key primordium for the brain reward circuitry, is unique among brain regions for its distinct pace of angiogenesis and selective vulnerability to hemorrhage during development. A major neonatal condition, GM hemorrhage can lead to cerebral palsy, hydrocephalus, and mental retardation. Here we identify a brain-region-specific neural progenitor-based signaling pathway dedicated to regulating GM vessel development. This pathway consists of cell-surface sphingosine-1-phosphate receptors, an intracellular cascade including Gα co-factor Ric8a and p38 MAPK, and target gene integrin ß8, which in turn regulates vascular TGF-ß signaling. These findings provide insights into region-specific specialization of neurovascular communication, with special implications for deciphering potent early-life endocrine, as well as potential gut microbiota impacts on brain reward circuitry. They also identify tissue-specific molecular targets for GM hemorrhage intervention.

A Tie2-driven BAC-TRAP transgenic line for in vivo endothelial gene profiling.

Recent technological innovations including bacterial artificial chromosome-based translating ribosome affinity purification (BAC-TRAP) have greatly facilitated analysis of cell type-specific gene expression in vivo, especially in the nervous system. To better study endothelial gene expression in vivo, we have generated a BAC-TRAP transgenic mouse line where the L10a ribosomal subunit is tagged with EGFP and placed under the control of the endothelium-specific Tie2 (Tek) promoter. We show that transgene expression in this line is widely, but specifically, detected in endothelial cells in several brain regions throughout pre- and postnatal development, as well as in other organs. We also show that this line results in highly significant enrichment of endothelium-specific mRNAs from brain tissues at different stages. This BAC-TRAP line therefore provides a useful genetic tool for in vivo endothelial gene profiling under various developmental, physiological, and pathological conditions. genesis 54:136-145, 2016. © 2016 Wiley Periodicals, Inc.

Regulation of the nascent brain vascular network by neural progenitors.

Neural progenitors are central players in the development of the brain neural circuitry. They not only produce the diverse neuronal and glial cell types in the brain, but also guide their migration in this process. Recent evidence indicates that neural progenitors also play a critical role in the development of the brain vascular network. At an early stage, neural progenitors have been found to facilitate the ingression of blood vessels from outside the neural tube, through VEGF and canonical Wnt signaling. Subsequently, neural progenitors directly communicate with endothelial cells to stabilize nascent brain vessels, in part through down-regulating Wnt pathway activity. Furthermore, neural progenitors promote nascent brain vessel integrity, through integrin αvß8-dependent TGFß signaling. In this review, we will discuss the evidence for, as well as questions that remain, regarding these novel roles of neural progenitors and the underlying mechanisms in their regulation of the nascent brain vascular network.

Prevalence of genetic variants associated with cardiovascular disease risk and drug response in the Southern Indian population of Kerala.

BACKGROUND AND AIM: This study reports the prevalence of five clinically significant variants associated with increased risk of cardiovascular disorders, and variable responses of individuals to commonly prescribed cardiovascular drugs in a South Indian population from the state of Kerala. MATERIALS AND METHODS: Genomic DNA isolated from 100 out-patient samples from Kerala were sequenced to examine the frequency of clinically relevant polymorphisms in the genes MYBPC3 (cardiomyopathy), SLCO1B1 (statin-induced myopathy), CYP2C9, VKORC1 (response to warfarin) and CYP2C19 (response to clopidogrel). RESULTS: Our analyses revealed the frequency of a 25 bp deletion variant of MYBPC3 associated with risk of cardiomyopathy was 7%, and the SLCO1B1 "C" allele associated with risk for statin-induced myopathy was 15% in this sample group. Among the other variants associated with dose-induced toxicity of warfarin, VKORC1 (c.1639G>A), was detected at 22%, while CYP2C9*3 and CYP2C9*2 alleles were present at a frequency of 15% and 3% respectively. Significantly, the tested sample population showed high prevalence (66%) of CYP2C19*2 variant, which determines response to clopidogrel therapy. CONCLUSIONS: We have identified that certain variants associated with cardiovascular disease and related drug response in the five genes, especially those in VKORC1, CYP2C19 and MYBPC3, are highly prevalent in the Kerala population, with almost 2 times higher prevalence of CYP2C19*2 variant compared with other regions in the country. Since the variants chosen in this study have relevance in disease phenotype and/or drug response, and are detected at a higher frequency, this study is likely to encourage clinicians to perform genetic testing before prescribing therapy.