Biomedical subjects

Alma Kuechler

Publications and source records attributed to Alma Kuechler.

2 recordsLinked to original sources

PubMed2026

Expanding the genotypic and phenotypic spectrum of PGAP1 deficiency: clinical and functional insights from 15 patients.

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are essential for neuronal development, synaptic organization and signaling. Defects in GPI-anchor biosynthesis or remodeling cause rare neurodevelopmental disorders, including post-GPI attachment to proteins 1 (PGAP1) deficiency. PGAP1 encodes an inositol deacylase required for GPI-anchor remodeling and appropriate trafficking and membrane localization of GPI-APs. Loss of PGAP1 function disrupts GPI-AP processing, but the clinical spectrum remains incompletely defined because reported cohorts are small. We report 15 individuals with biallelic PGAP1 variants from 11 unrelated families identified through international collaboration. Clinical information was collected using a standardized phenotyping questionnaire and review of available clinical records. The most frequently recorded features were developmental delay or intellectual disability, motor developmental delay, speech impairment, facial dysmorphism, hypotonia and seizures. Independent walking was clearly recorded in a minority of individuals, while feeding, ophthalmological, musculoskeletal and neuroimaging findings were recorded in subsets of the cohort. Clinical investigations were performed as part of routine care and were not uniform across sites. Accordingly, source-dependent assessments including MRI, EEG, EMG/NCS, formal ophthalmology, hearing assessment, systemic imaging, IQ/DQ testing, MRC scoring and anthropometric Z-scores are reported descriptively or using available-data denominators. Spasticity, hypertonia or possible peripheral nerve involvement was recorded in some clinical summaries; however, electrophysiological confirmation was not uniformly available, and confirmed peripheral neuropathy was not analyzed as a cohort-level prevalence outcome. Functional studies in selected patient-derived cells or model systems demonstrated PI-PLC resistance of GPI-APs, supporting impaired GPI-anchor remodeling. These findings expand the genotypic and recorded phenotypic spectrum of PGAP1 deficiency.

Journal Article↗

PubMed2025

DNA-binding affinity and specificity determine the phenotypic diversity in BCL11B-related disorders.

BCL11B is a Cys2-His2 zinc-finger (C2H2-ZnF) domain-containing, DNA-binding, transcription factor with established roles in the development of various organs and tissues, primarily the immune and nervous systems. BCL11B germline variants have been associated with a variety of developmental syndromes. However, genotype-phenotype correlations along with pathophysiologic mechanisms of selected variants mostly remain elusive. To dissect these, we performed genotype-phenotype correlations of 92 affected individuals harboring a pathogenic or likely pathogenic BCL11B variant, followed by immune phenotyping, analysis of chromatin immunoprecipitation DNA-sequencing data, dual-luciferase reporter assays, and molecular modeling. These integrative analyses enabled us to define three clinical subtypes of BCL11B-related disorders. It is likely that gene-disruptive BCL11B variants and missense variants affecting zinc-binding cysteine and histidine residues cause mild to moderate neurodevelopmental delay with increased propensity for behavioral and dental anomalies, allergies and asthma, and reduced type 2 innate lymphoid cells. Missense variants within C2H2-ZnF DNA-contacting α helices cause highly variable clinical presentations ranging from multisystem anomalies with demise in the first years of life to late-onset, hyperkinetic movement disorder with poor fine motor skills. Those not in direct DNA contact cause a milder phenotype through reduced, target-specific transcriptional activity. However, missense variants affecting C2H2-ZnFs, DNA binding, and "specificity residues" impair BCL11B transcriptional activity in a target-specific, dominant-negative manner along with aberrant regulation of alternative DNA targets, resulting in more severe and unpredictable clinical outcomes. Taken together, we suggest that the phenotypic severity and variability is largely dependent on the DNA-binding affinity and specificity of altered BCL11B proteins.

Adolescent↗