Case report: Genotype and phenotype of DYNC1H1-related malformations of cortical development: a case report and literature review

[A variant of p.Arg1623Gln of the DYNC1H1 gene in a patient with corpus callosum agenesis, polydactyly, mental development disorder, and neuromuscular system disorders]

DYNC1H1 encodes the heavy chain of dynein 1, a protein that plays a critical role in intracellular transport and is also involved in neurogenesis, bipolar spindle apparatus formation, and interaction with certain regulatory proteins. Many variants of the gene are described in various neuromuscular, psychoneurological, congenital abnormalities, and malignancies. In this clinical case, the correlation of clinical manifestations with molecular genetic changes of the DYNC1H1 gene was evaluated. A variant was identified and presented de novo in the linker domain of the protein in a patient with abnormalities of brain development (pachygyria of the temporal and frontal lobes, polymicrogyria of the occipital lobes, cerebellar agenesis), polydactylitis, mental development disorder, and involvement of the neuromuscular system, as well as congenital cataracts. In this case, a new feature is described - polydactyly - not previously described in the variant c.4868G>A (p.Arg1623Gln), which expands the range of clinical manifestations and can contribute to the understanding of the mechanisms of phenotypic heterogeneity, as well as the development of optimal diagnostic algorithms.

Presynaptic perspective: Axonal transport defects in neurodevelopmental disorders

Disruption of synapse assembly and maturation leads to a broad spectrum of neurodevelopmental disorders. Presynaptic proteins are largely synthesized in the soma, where they are packaged into precursor vesicles and transported into distal axons to ensure precise assembly and maintenance of presynapses. Due to their morphological features, neurons face challenges in the delivery of presynaptic cargos to nascent boutons. Thus, targeted axonal transport is vital to build functional synapses. A growing number of mutations in genes encoding the transport machinery have been linked to neurodevelopmental disorders. Emerging lines of evidence have started to uncover presynaptic mechanisms underlying axonal transport defects, thus broadening the view of neurodevelopmental disorders beyond postsynaptic mechanisms. In this review, we discuss presynaptic perspectives of neurodevelopmental disorders by focusing on impaired axonal transport and disturbed assembly and maintenance of presynapses. We also discuss potential strategies for restoring axonal transport as an early therapeutic intervention.