The Study on the Clinical Phenotype and Function of HPRT1 Gene

Background: Lesch-Nyhan disease (LND) is a rare x-linked purine metabolic neurogenetic disease caused by enzyme hypoxanthine-guanine phosphoriribosyltransferase(HGprt) deficiency, also known as self-destructive appearance syndrome. A series of manifestations are caused by abnormal purine metabolism. The typical clinical manifestations are hyperuricemia, growth retardation, mental retardation, short stature, dance-like athetosis, aggressive behavior, and compulsive self-harm.. Results: we identified a point mutation c.151C > T (p. Arg51*) in a pedigree. We analyzed the clinical characteristics of children in a family, and obtained the blood of their parents and siblings for second-generation sequencing. At the same time, we also analyzed and compared the expression of HPRT1 gene and predicted the three-dimensional structure of the protein. And we analyzed the clinical manifestations caused by the defect of the HPRT1 genethe mutation led to the termination of transcription at the 51st arginine, resulting in the production of truncated protein, and the relative expression of HPRT1 gene in patients was significantly lower than other family members and 10 normal individuals. Conclusion: this mutation leads to the early termination of protein translation and the formation of a truncated HPRT protein, which affects the function of the protein and generates corresponding clinical manifestations.

Patterns of Inheritance in Neurogenetic Disease

The human genome consists of approximately 22,000 genes that are encoded within the nuclear DNA and embedded in the chromosome. Mitochondria are the only cytoplasmic organelles that have their own DNA. Nuclear gene disorders and mitochondrial inheritance are discussed in this chapter. Nuclear gene disorders follow the patterns of inheritance originally described by Gregor Mendel. They often are referred to as single-gene disorders because 1 or more alleles of only 1 locus are the major determinants of phenotype.

Spinocerebellar Ataxia Type 28 in a Chinese Pedigree: A Case Report and Literature Review

Spinocerebellar ataxia (SCA) is a common neurogenetic disease, which mainly manifests as ataxia of posture, gait and limbs, cerebellar dysarthria, cerebellar and supranuclear eye movement disorders. It is found that SCA is a kind of progressive neurodegenerative disease including many subtypes, which is mainly mapped to two genetic patterns as: autosomal dominant cerebellar ataxia (ADCA) and autosomal recessive cerebellar ataxia (ARCA). Molecular genetic diagnosis functions as a necessity in its clinical diagnosis and treatment. In our previous clinical work, we found a family with ataxia who presented a c.1852A > G missense mutation in the exon region of AFG3L2 gene by whole exome sequencing (WES) and Sanger validation. Spinocerebellar ataxia type 28 (SCA28) was suspected, which was not reported in the previous literature. We here report the case and review the literature.

Hereditary Myelopathies

Hereditary myelopathies are an important and likely underappreciated component of neurogenetic disease. While previously distinctions have been made by age of onset, the growing power and availability of high-quality neuroimaging and next-generation sequencing are increasingly expanding classical phenotypes and diminishing the utility of age-based classifications. Increasingly, cases of “atypical” disease presentations are challenging past assumptions regarding the age of onset and survival in many disorders and identifying allelic syndromes in others. Despite this, there is poor awareness of the potential for spinal involvement in many diseases that typically affect the brain. Broadly speaking, congenital myelopathies can be neuroanatomically grouped into motor neuron, axonopathy, spinocerebellar, cerebroleukodystrophy, and pan-neuraxis (generally central nervous system predominant with associated axonopathy) disorders.Here, we review hereditary causes of myelopathy, organized by neuroanatomy, and highlight atypical presentations. We discuss findings concerning an underlying genetic etiology for myelopathy, as well as practical, technical, and ethical considerations of diagnostic genetic testing.

Future Prospects of Gene Therapy for Friedreich’s Ataxia

Friedreich’s ataxia is an autosomal recessive neurogenetic disease that is mainly associated with atrophy of the spinal cord and progressive neurodegeneration in the cerebellum. The disease is caused by a GAA-expansion in the first intron of the frataxin gene leading to a decreased level of frataxin protein, which results in mitochondrial dysfunction. Currently, there is no effective treatment to delay neurodegeneration in Friedreich’s ataxia. A plausible therapeutic approach is gene therapy. Indeed, Friedreich’s ataxia mouse models have been treated with viral vectors en-coding for either FXN or neurotrophins, such as brain-derived neurotrophic factor showing promising results. Thus, gene therapy is increasingly consolidating as one of the most promising therapies. However, several hurdles have to be overcome, including immunotoxicity and pheno-toxicity. We review the state of the art of gene therapy in Friedreich’s ataxia, addressing the main challenges and the most feasible solutions for them.

Neurogenetic fetal akinesia and arthrogryposis: genetics, expanding genotype-phenotypes and functional genomics

BackgroundFetal akinesia and arthrogryposis are clinically and genetically heterogeneous and have traditionally been refractive to genetic diagnosis. The widespread availability of affordable genome-wide sequencing has facilitated accurate genetic diagnosis and gene discovery in these conditions.MethodsWe performed next generation sequencing (NGS) in 190 probands with a diagnosis of arthrogryposis multiplex congenita, distal arthrogryposis, fetal akinesia deformation sequence or multiple pterygium syndrome. This sequencing was a combination of bespoke neurogenetic disease gene panels and whole exome sequencing. Only class 4 and 5 variants were reported, except for two cases where the identified variants of unknown significance (VUS) are most likely to be causative for the observed phenotype. Co-segregation studies and confirmation of variants identified by NGS were performed where possible. Functional genomics was performed as required.ResultsOf the 190 probands, 81 received an accurate genetic diagnosis. All except two of these cases harboured class 4 and/or 5 variants based on the American College of Medical Genetics and Genomics guidelines. We identified phenotypic expansions associated with CACNA1S, CHRNB1, GMPPB and STAC3. We describe a total of 50 novel variants, including a novel missense variant in the recently identified gene for arthrogryposis with brain malformations—SMPD4.ConclusionsComprehensive gene panels give a diagnosis for a substantial proportion (42%) of fetal akinesia and arthrogryposis cases, even in an unselected cohort. Recently identified genes account for a relatively large proportion, 32%, of the diagnoses. Diagnostic-research collaboration was critical to the diagnosis and variant interpretation in many cases, facilitated genotype-phenotype expansions and reclassified VUS through functional genomics.