Browsing by Author "Johannesen, Katrine"

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    SLC6A1 variant pathogenicity, molecular function and phenotype: a genetic and clinical analysis
    (2023) Stefanski, Arthur; Pérez Palma, Eduardo; Brünger, Tobias; Montanucci, Ludovica; Gati, Cornelius; Klöckner, Chiara; Johannesen, Katrine; Goodspeed, Kimberly; Macnee, Marie; Deng, Alexander; Aledo, Ángel; Borovikov,Artem; Kava, Maina; Bouman, Arjan; Hajianpour, M.; Pal, Deb; Engelen, Marc; Hagebeuk, Eveline; Shinawi, Marwan; Heidlebaugh, Alexis; Oetjens, Kathryn; Hoffman, Trevor; Striano, Pasquale; Freed, Amanda; Futtrup, Line; Balslev, Thomas; Abulí, Anna; Danvoye, Leslie; Lederer, Damien; Balci, Tugce; Nabavi, Maryam; Butler, Elizabeth; Drewes, Sarah; Van Engelen, Kalene; Howell, Katherine; Khoury, Jean; May, Patrick; Trinidad, Marena; Froelich, Steven; Lemke, Johannes
    Genetic variants in the SLC6A1 gene can cause a broad phenotypic disease spectrum by altering the protein function. Thus, systematically curated clinically relevant genotype-phenotype associations are needed to understand the disease mechanism and improve therapeutic decision-making. We aggregated genetic and clinical data from 172 individuals with likely pathogenic/pathogenic (lp/p) SLC6A1 variants and functional data for 184 variants (14.1% lp/p). Clinical and functional data were available for a subset of 126 individuals. We explored the potential associations of variant positions on the GAT1 3D structure with variant pathogenicity, altered molecular function and phenotype severity using bioinformatic approaches. The GAT1 transmembrane domains 1, 6 and extracellular loop 4 (EL4) were enriched for patient over population variants. Across functionally tested missense variants (n = 156), the spatial proximity from the ligand was associated with loss-of-function in the GAT1 transporter activity. For variants with complete loss of in vitro GABA uptake, we found a 4.6-fold enrichment in patients having severe disease versus non-severe disease (P = 2.9 × 10-3, 95% confidence interval: 1.5-15.3). In summary, we delineated associations between the 3D structure and variant pathogenicity, variant function and phenotype in SLC6A1-related disorders. This knowledge supports biology-informed variant interpretation and research on GAT1 function. All our data can be interactively explored in the SLC6A1 portal (https://slc6a1-portal.broadinstitute.org/).
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    Structural mapping of GABRB3 variants reveals genotype-phenotype correlations
    (2021) Johannesen, Katrine; Iqba, Sumaiya; Guazz, Milena; Mohammadi, Nazanin; Pérez, Eduardo; Schaefer, Elise; De Saint Martin, Anne; Abiwarde, Marie; McTague, Amy; Pons, Roser; Piton, Amelie; Kurian, Manju; Ambegaonkar, Gautam; Firth, Helen; Sanchis, Alba; Deprez, Marie; Jansen, Katrien; De Waele, Liesbeth; Briltra, Eva; Verbeek, Nienke; Van Kempen, Marjan; Fazeli, Walid; Striano, Pasquale; Zara, Federico; Visser, Gerhard; Braakman, Hilde; Haeusle, Martin; Elbracht, Miriam; Vahe, Ulvi; Smol, Thomas; Lemke, Johannes; Platzer, Konrad; Kennedy, Joanna; Martin, Karl; Ping, Billie; Smyth, Kimberly; Kaplan, Julie; Thomas, Morgan; Dewenter, Malin; Dinopoulos, Argirios; Campbell, Arthur; Lal, Dennis; Lederer, Damien; Liao, Vivian; Ahring, Philip; Møller, Rikke; Gardella, Elena
    Purpose: Pathogenic variants in GABRB3 have been associated with a spectrum of phenotypes from severe developmental disorders and epileptic encephalopathies to milder epilepsy syndromes and mild intellectual disability (ID). In this study, we analyzed a large cohort of individuals with GABRB3 variants to deepen the phenotypic understanding and investigate genotype-phenotype correlations. Methods: Through an international collaboration, we analyzed electro-clinical data of unpublished individuals with variants in GABRB3, and we reviewed previously published cases. All missense variants were mapped onto the 3-dimensional structure of the GABRB3 subunit, and clinical phenotypes associated with the different key structural domains were investigated. Results: We characterized 71 individuals with GABRB3 variants, including 22 novel subjects, expressing a wide spectrum of phenotypes. Interestingly, phenotypes correlated with structural locations of the variants. Generalized epilepsy, with a median age at onset of 12 months, and mild-to-moderate ID were associated with variants in the extracellular domain. Focal epilepsy with earlier onset (median: age 4 months) and severe ID were associated with variants in both the pore-lining helical transmembrane domain and the extracellular domain. Conclusion: These genotype-phenotype correlations will aid the genetic counseling and treatment of individuals affected by GABRB3-related disorders. Future studies may reveal whether functional differences underlie the phenotypic differences.

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