PURPOSE: This study aims to comprehensively delineate the phenotypic spectrum of ACTL6B-related disorders, previously associated with both autosomal recessive and autosomal dominant neurodevelopmental disorders. Molecularly, the role of the nucleolar protein ACTL6B in contributing to the disease has remained unclear. METHODS: We identified 105 affected individuals, including 39 previously reported cases, and systematically analyzed detailed clinical and genetic data for all individuals. Additionally, we conducted knockdown experiments in neuronal cells to investigate the role of ACTL6B in ribosome biogenesis. RESULTS: Biallelic variants in ACTL6B are associated with severe-to-profound global developmental delay/intellectual disability, infantile intractable seizures, absent speech, autistic features, dystonia, and increased lethality. De novo monoallelic variants result in moderate-to-severe global developmental delay/intellectual disability, absent speech, and autistic features, whereas seizures and dystonia were less frequently observed. Dysmorphic facial features and brain abnormalities, including hypoplastic corpus callosum, and parenchymal volume loss/atrophy, are common findings in both groups. We reveal that in the nucleolus, ACTL6B plays a crucial role in ribosome biogenesis, particularly in pre-rRNA processing. CONCLUSION: This study provides a comprehensive characterization of the clinical spectrum of both autosomal recessive and dominant forms of ACTL6B-associated disorders. It offers a comparative analysis of their respective phenotypes provides a plausible molecular explanation and suggests their inclusion within the expanding category of "ribosomopathies."

• Klíčová slova
• ACTL6B, Autism, BAFopathies, Epileptic-dyskinetic encephalopathy, Ribosomopathies,
• MeSH
• dítě MeSH
• dominantní geny MeSH
• fenotyp MeSH
• geny recesivní MeSH
• jaderné proteiny * genetika   MeSH
• kojenec MeSH
• lidé MeSH
• mentální retardace genetika   patologie   MeSH
• mladiství MeSH
• mozek patologie   MeSH
• mutace MeSH
• nemoci mozku * genetika   patologie   MeSH
• neurovývojové poruchy * genetika   MeSH
• předškolní dítě MeSH
• vývojové poruchy u dětí * genetika   patologie   MeSH
• Check Tag
• dítě MeSH
• kojenec MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• jaderné proteiny * MeSH

CONTEXT: 4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date. OBJECTIVE: To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy. DESIGN: An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated. SETTING: This was a multicenter retrospective study using information collected from 3 predominant centers. PATIENTS: A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included. MAIN OUTCOME MEASURES: Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts. RESULTS: The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients. CONCLUSIONS: Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder.

• Klíčová slova
• 4H leukodystrophy, POLR3-related leukodystrophy, hypogonadotropic hypogonadism, hypomyelination,
• MeSH
• biologická variabilita populace MeSH
• dědičné demyelinizační nemoci CNS komplikace   epidemiologie   genetika   MeSH
• dítě MeSH
• DNA řízené RNA-polymerasy genetika   MeSH
• dospělí MeSH
• genetická heterogenita MeSH
• hypogonadismus epidemiologie   etiologie   MeSH
• kohortové studie MeSH
• kojenec MeSH
• lidé MeSH
• mitochondriální nemoci komplikace   epidemiologie   genetika   MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mutace MeSH
• nemoci endokrinního systému epidemiologie   etiologie   genetika   MeSH
• novorozenec MeSH
• poruchy růstu epidemiologie   etiologie   genetika   MeSH
• předškolní dítě MeSH
• průřezové studie MeSH
• retrospektivní studie MeSH
• RNA-polymerasa III genetika   MeSH
• Check Tag
• dítě MeSH
• dospělí MeSH
• kojenec MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• novorozenec MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• multicentrická studie MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• DNA řízené RNA-polymerasy MeSH
• POLR1C protein, human MeSH Prohlížeč
• POLR3A protein, human MeSH Prohlížeč
• POLR3B protein, human MeSH Prohlížeč
• RNA-polymerasa III MeSH