Biology subjects

Helman, G.

Publications and source records attributed to Helman, G..

3 recordsLinked to original sources

bioRxiv2022

mRNA-based vaccines against SARS-CoV-2 do not stimulate interferon stimulatory gene expression in individuals affected by Aicardi Goutieres Syndrome.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses threats to individuals with rare disease, in part because so little is known about the impact of COVID-19 infection and vaccination safety in rare disease populations. Of particular concern, given the overlap in disease manifestations and interferon dysregulation, are a group of heritable autoinflammatory conditions called type I interferonopathies. The most common of these, Aicardi Goutieres Syndrome (AGS), is caused by altered nucleic acid metabolism and sensing, resulting in additional concerns surrounding the use of mRNA vaccination approaches. To determine whether mRNA vaccines induce an interferon response in AGS, we applied mRNA SARS-CoV-2 vaccines to whole blood samples and assessed internalization and interferon signaling gene expression responses to the mRNA. In all cases (11 AGS and 11 control samples), interferon signatures did not significantly increase from baseline, regardless of baricitinib treatment status in the AGS subjects, and were even decreased, when using codon optimized SARS-CoV-2 di-proline modified spike sequence (S2P). Internalization of S2P in human dendritic cells was verified by Western Blot, and in control and AGS blood cells was verified by Luciferase activity. Although numbers of tested samples in this rare disease are small, based on these findings, we suggest that COVID vaccination is unlikely to directly stimulate the interferon signaling gene expression in AGS patients via response to mRNA internalization. The in vitro nature of this study cannot exclude an exaggerated interferon response to spike protein production at a systemic level in individuals with a primary heritable interferonopathy. In the context of continued SARS-CoV-2 spread in the community, we do not recommend withholding vaccination in this rare disease group. However, we recommend that vaccinations for AGS patients are provided in a controlled setting with appropriate observation and used with caution in individuals with prior vaccine associated adverse events.

immunology↗

bioRxiv2019

Type II Alexander disease caused by splicing errors and aberrant overexpression of an uncharacterized GFAP isoform.

Alexander disease results from gain of function mutations in the gene encoding glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed in astrocytes. At least eight GFAP isoforms have been described, however, the predominant alpha isoform accounts for approximately 90% of GFAP protein in the central nervous system. Here we describe exonic variants identified in three unrelated families with Type II Alexander disease that alter the splicing of GFAP pre-mRNA and result in upregulation of a previously uncharacterized GFAP lambda isoform (NM 001363846.1). Affected members of Family 1 and Family 2 shared the same missense variant, NM 001363846.1:c.1289G>A;p.(Arg430His) while in Family 3 we identified a synonymous variant in the adjacent nucleotide, NM 001363846.1:c.1290C>A;p.(Arg430Arg). Using RNA and protein analysis of brain autopsy samples, and a mini-gene splicing reporter assay, we demonstrate both variants result in upregulation of the lambda isoform. We assessed other GFAP variants in the ClinVar database for predicted aberrant splicing and using the same assay demonstrated significant changes to splicing for two selected variants. Our approach demonstrates the importance of characterizing the effect of GFAP variants on mRNA splicing in order to inform future pathophysiologic and therapeutic study for Alexander disease.

genetics↗

bioRxiv2019

Heterozygous variants in the mechanosensitive ion channel TMEM63A result in transient hypomyelination during infancy

Mechanically activated (MA) ion channels convert physical forces into electrical signals. Despite the importance of this function, the involvement of mechanosensitive ion channels in human disease is poorly understood. Here we report heterozygous missense mutations in the gene encoding the MA ion channel TMEM63A that result in an infantile disorder resembling a hypomyelinating leukodystrophy. Four unrelated individuals presented with congenital nystagmus, motor delay, and deficient myelination on serial scans in infancy, prompting the diagnosis of Pelizaeus-Merzbacher (like) disease. Genomic sequencing revealed all four individuals carry heterozygous missense variants in the pore-forming domain of TMEM63A. These variants were confirmed to have arisen de novo in three of the four individuals. While the physiological role of TMEM63A is incompletely understood, it is highly expressed in oligodendrocytes and it has recently been shown to be a mechanically activated (MA) ion channel. Using patch clamp electrophysiology, we demonstrated that each of the modelled variants results in strongly attenuated stretch-activated currents when expressed in naive cells. Unexpectedly, the clinical evolution of all four individuals has been surprisingly favorable, with substantial improvements in neurological signs and developmental progression. In the three individuals with follow-up scans after four years of age, the myelin deficit had almost completely resolved. Our results suggest a previously unappreciated role for mechanosensitive ion channels in myelin development.

genomics↗