Simran Samra

Samra, Sharma, et al. identify biallelic loss-of-function variants in OSMR as the cause of a new human primary atopic disorder characterized by severe early-onset eczema, eosinophilia, and elevated IgE. Loss of OSMRβ surface expression abolishes OSM-dependent STAT signaling, revealing a key role for OSM-OSMR signaling in maintaining cutaneous immune homeostasis.

Carpenter syndrome type 2 (CRPT2) is a rare autosomal recessive disease mainly characterized by craniosynostosis and polysyndactyly. CRPT2 is the rarer subtype of Carpenter syndrome (CRPTS) and is caused by biallelic variants in the multiple epidermal growth factor‐like domains 8 gene ( MEGF8 ). Due to its rarity and phenotypic overlap with other craniosynostosis syndromes, definitive molecular diagnosis of CRPT2 can be challenging. Here, we describe a proband with CRPT2 carrying compound heterozygous variants in MEGF8 : one de novo variant disrupting splicing and a maternally inherited missense variant. To resolve these variants, we leveraged long‐read genome sequencing to phase the missense variant alleles and RNA sequencing to determine splicing impact. This case highlights the diagnostic value of using sequencing methods beyond the more conventional short‐read exome sequencing. Our findings expand the spectrum of MEGF8 variants causing CRPT2 and underscore the utility of emerging sequencing technologies in elucidating complex or previously unresolved genotypes. Expanding access to such technologies is anticipated to accelerate rare disease diagnosis and deepen our understanding of the genetic mechanisms underlying these conditions.

OSMRβ (Oncostatin M receptor beta), a member of the IL-6 superfamily of cell surface receptors, binds OSM and IL-31 and plays a critical role in human immunity. We identified probands from four kindreds with biallelic damaging variants in OSMR , which encodes OSMRβ. Patients had a unifying phenotype for severe widespread, early-onset atopic dermatitis, peripheral eosinophilia, and elevated serum IgE. Patient OSMRβ variants were not appropriately expressed on the cell surface compared to OSMRβ ^WT . Patient OSMR variants showed significantly reduced OSM-mediated activation of STAT1, STAT3, and STAT5 and distinct transcriptional changes in primary dermal fibroblasts, including loss of interferon and inflammatory signatures. These defects were rescued upon lentiviral transduction of WT- OSMR . Together, these data establish that human germline biallelic loss-of-function OSMR variants cause severe allergic disease. We anticipate that this discovery will facilitate the recognition of additional affected individuals and the full definition of this novel primary atopic disorder.

Inborn errors of immunity (IEIs) are caused by deleterious variants in immune-related genes. ASXL1 is an epigenetic modifier not previously linked to an IEI. Clonal hematopoiesis and hematologic neoplasms often feature somatic ASXL1 variants, and Bohring–Opitz syndrome, a neurodevelopmental disorder, is caused by heterozygous truncating ASXL1 variants. We present an IEI caused by biallelic germline missense variants in ASXL1. The patient had a history of hematologic abnormalities and viral-associated complications, including chronic macrocytosis, persistent vaccine-strain rubella granulomas, and EBV-associated Hodgkin lymphoma. Immunophenotyping revealed loss of B cells, hypogammaglobulinemia, and impairments in cytotoxic T and NK cell populations. T cells exhibited skewing toward an exhausted memory phenotype, global DNA methylation loss, and increased epigenetic aging. These aberrations were ameliorated by wild-type ASXL1 transduction, confirming the patient variants’ pathogenicity. This study defines a novel human IEI caused by ASXL1 deficiency, a diagnosis that should be considered in individuals with chronic viral infections, viral-associated malignancies, and combined immune deficiency.

ThPOK is a transcription factor that acts as a master regulator of CD4+ T cell lineage commitment. We report the first human disease caused by a genetic alteration in ThPOK, specifically, a damaging heterozygous de novo variant in ThPOK (NM_001256455.2:c.1080A>C, p.K360N). This patient exhibited the unusual constellation of persistent CD4+ T cell deficiency, allergy, interstitial lung disease, corneal vascularization and scarring, developmental delay, and growth failure. The ThPOKK360N variant displayed abnormal multimorphic activity, interfering with ThPOKWT (antimorph), failing to bind wild-type ThPOK consensus sequences (amorph), and showing novel DNA-binding specificity (neomorph). Single-cell RNA sequencing revealed defects in CD4+ and CD8+ T cell maturation and activation (hypomorph). Recapitulated in lentivirally transduced healthy control T cells and fibroblasts, the transcriptomic analysis showed ThPOKK360N-transduced T cells had impaired TCR activation and ThPOKK360N-transduced fibroblasts with increased profibrotic gene expression. This novel human disease confirms ThPOK’s role in CD4+ T cell development but also uncovers novel roles in TCR activation and regulation of fibrotic pathways in fibroblasts.

ThPOK is best known as a regulator of CD4+ T cell lineage commitment, although it was initially cloned as a suppressor of collagen expression in the skin. The role of ThPOK has not been formally established in humans since individuals with damaging variants in ThPOK have not yet been identified. Here, we report the first case of a human with a damaging heterozygous de novo variant in ThPOK causing a syndrome encompassing CD4+ T cell deficiency, allergy, fibroinflammatory interstitial lung disease, developmental delay, and growth failure. The patient variant, ThPOK K360N, exhibited abnormal multimorphic activity, including interfering with ThPOK WT in regulating gene regulation (antimorph). Protein-DNA interaction assays showed inability of ThPOK K360N to bind to wild-type consensus sequences (amorph) and revealed a novel DNA-binding specificity (neomorph). Single-cell RNA sequencing of peripheral blood revealed potential developmental defects in maturation and activation of CD4+ and CD8+ T cells (hypomorph). To establish causality, we recapitulated the observed cellular defects in lentivirally transduced healthy control T cells and pulmonary fibroblasts. Transcriptomic analysis showed that T cells transduced with ThPOK K360N lacked the upregulation of activation, proliferation, and functional pathways observed in ThPOKWT-transduced cells. When overexpressed in healthy control fibroblasts, ThPOK K360N significantly increased the expression of pro-fibrotic genes implicated in pulmonary fibrosis, indicating a defect in regulating collagen expression. This novel human disease caused by a multimorphic variant in ThPOK confirms its role in CD4+ T cell development in an intact human context, while also revealing an unanticipated role for ThPOK in T cell function and the regulation of fibrotic pathways in fibroblasts.

Microtubule affinity regulating kinase 4 (MARK4) is a serine/threonine kinase that plays a key role in tau phosphorylation and regulation of the mTOR pathway. Abnormal tau phosphorylation and dysregulation of the mTOR pathway are implicated in neurodegenerative and neurodevelopmental disorders. Here, we report a novel gain-of-function variant in MARK4 in two siblings with childhood-onset neurodevelopmental disability and dysmorphic features. The siblings carry a germline heterozygous missense MARK4 variant c.604T>C; p.Phe202Leu, located in the catalytic domain of the kinase, which they inherited from their unaffected, somatic mosaic mother. Functional studies show that this amino acid substitution has no impact on protein expression but instead increases the ability of MARK4 to phosphorylate tau isoforms found in the fetal and adult brain. The MARK4 variant also increases phosphorylation of ribosomal protein S6, indicating upregulation of the mTORC1 pathway. This is the first study to link a germline monoallelic MARK4 variant to a childhood-onset neurodevelopmental disorder characterized by global developmental delay, intellectual disability, behavioral abnormalities, and dysmorphic features.