Weiwei Li

• Lehtonen, Johanna; Hakonen, Anna H; Hassinen, Antti; Lurås, Sanne Iversen; Kaustio, Meri & Glumoff, Virpi [Show all 19 contributors for this article] (2025). Genome sequencing reveals CCDC88A variants in malformations of cortical development and immune dysfunction. Human Molecular Genetics. ISSN 0964-6906. 34(15), p. 1294–1312. doi: 10.1093/hmg/ddaf081. Full text in Research Archive Show summary

  Abstract Malformations of cortical development (MCDs) encompass a diverse group of genetic and clinical disorders. Here, we aimed to determine a genetic etiology for two siblings manifesting MCD, microcephaly, epilepsy, intellectual disability, and susceptibility to infections. A missense variant (NM_018084:c.929A > C, p.Asp310Ala) and an intragenic deletion (exons 14–16) in CCDC88A were identified as compound heterozygous in patients by genome sequencing. Truncating homozygous CCDC88A variants are known to cause an ultra-rare syndrome manifesting with MCD, microcephaly, seizures, and severe neurological impairment. CCDC88A encodes girdin, which is essential for various cell functions, such as actin remodeling and cell proliferation. Western blot analysis showed that the missense variant allele was expressed in fibroblasts at a level compatible with a heterozygous allele, whereas a truncated protein from the deletion allele was barely detectable. Proliferation and wound-healing assays revealed that girdin-deficient fibroblasts proliferated faster and migrated slower than controls. High-content imaging highlighted girdin-deficient fibroblasts as smaller and their actin remodeling disrupted, leading to perinuclear accumulation of endolysosomal organelles. To confirm these cellular phenotypes resulted from girdin loss, CRISPR-Cas9 edited knockout models of healthy fibroblasts were created, replicating the observations in patient cells. Additionally, the siblings exhibited reduced monocytoid and plasmacytoid dendritic cells, suggesting compromised immunity due to girdin deficiency. In summary, the study describes the first case of a CCDC88A missense variant and intragenic deletion associated with MCD. It demonstrates altered immunity and girdin-related cellular changes, such as cell morphology and proliferation-migration dichotomy, in patient and knockout fibroblasts, reinforcing the pathogenic relevance of these variants.

• Kaustio, Meri; Szymanska, Monika; Li, Weiwei; Braathen, Ragnhild Selvig; Campbell, Tessa M. & Haugen, Frida Loe [Show all 23 contributors for this article] (2025). Heterozygous loss of MAP4K1 causes immune dysregulation by amplifying T-cell responses. Journal of Allergy and Clinical Immunology. ISSN 0091-6749. 156(4), p. 1024–1037. doi: 10.1016/j.jaci.2025.07.010. Full text in Research Archive Show summary

  Background MAP4K1 encodes hematopoietic progenitor kinase 1 (HPK1), a serine/threonine kinase that negatively regulates T-cell receptor signaling via phosphorylation of the adaptor proteins SLP-76 (Src homology 2 domain-containing leukocyte protein of 76 kDa) and Gads. While common MAP4K1 variants have been implicated in polygenic immune-mediated diseases, the impact of rare germline variants on human immunity remains undefined. Objective We investigated the immunologic and functional consequences of HPK1 deficiency in individuals with suspected inborn errors of immunity. Methods We performed genomic linkage analysis and exome sequencing to identify disease-associated variants in patients with inborn errors of immunity. Immunophenotyping, RNA sequencing, and functional assays were conducted on patient-derived lymphocytes, complemented by CRISPR-Cas9–mediated MAP4K1 disruption and correction in primary T cells. Results Heterozygous MAP4K1 loss-of-function variants were identified in two kindreds presenting with diverse immune dysregulatory symptoms, including recurrent fevers, inflammatory arthritis, Epstein-Barr virus–related complications, and nephritis. These variants led to reduced HPK1 protein levels and SLP-76Ser376 phosphorylation. While lymphocyte development was largely preserved, T cells from HPK1-deficient individuals displayed hyperresponsiveness to T-cell receptor stimulation, characterized by elevated secretion of proinflammatory cytokines, particularly IFN-γ and TNF. CRISPR-Cas9–mediated knockout recapitulated, and variant correction partially reversed this phenotype. Transcriptomic profiling of stimulated CD4+ T cells further revealed upregulation of immune signaling pathways—including NF-κB, JAK/STAT, and AP-1—as well as increased expression of multiple T-cell cytokines, consistent with enhanced T-cell receptor signaling and T-cell responses in HPK1-deficient individuals. Conclusion HPK1 deficiency, caused by heterozygous loss of MAP4K1, is a novel monogenic cause of immune dysregulation. Increased T-cell activation and proinflammatory cytokine production are implicated in disease pathogenesis

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