Focus Area Tag: Neurogenomics

Orphanet J Rare Dis. 2020 May 26;15(1):126. doi: 10.1186/s13023-020-01379-8. ABSTRACT BACKGROUND: Tetrahydrobiopterin (BH₄) deficiencies comprise a group of six rare neurometabolic disorders characterized by insufficient synthesis of the monoamine neurotransmitters dopamine and serotonin due to a disturbance of BH₄ biosynthesis or recycling. Hyperphenylalaninemia (HPA) is the first diagnostic hallmark for most BH₄ deficiencies, apart from autosomal dominant guanosine triphosphate cyclohydrolase I deficiency and sepiapterin reductase deficiency. Early supplementation of neurotransmitter precursors and where appropriate, treatment of HPA results in significant improvement of motor and cognitive function. Management approaches differ across the world and therefore these guidelines have been developed aiming to harmonize and optimize patient care. Representatives of the International Working Group on Neurotransmitter related Disorders (iNTD) developed the guidelines according to the SIGN (Scottish Intercollegiate Guidelines Network) methodology by evaluating all available evidence for the diagnosis and treatment of BH₄ deficiencies. CONCLUSION: Although the total body of evidence in the literature was mainly rated as low or very low, these consensus guidelines will help to harmonize clinical practice and to standardize and improve care for BH₄ deficient patients. PMID:32456656 | PMC:PMC7251883 | DOI:10.1186/s13023-020-01379-8

Trends Neurosci. 2020 Jul;43(7):519-532. doi: 10.1016/j.tins.2020.04.009. Epub 2020 May 15. ABSTRACT Neural tube defects (NTDs) represent a failure of the neural plate to complete the developmental transition to a neural tube. NTDs are the most common birth anomaly of the CNS. Following mandatory folic acid fortification of dietary grains, a dramatic reduction in the incidence of NTDs was observed in areas where the policy was implemented, yet the genetic drivers of NTDs in humans, and the mechanisms by which folic acid prevents disease, remain disputed. Here, we discuss current understanding of human NTD genetics, recent advances regarding potential mechanisms by which folic acid might modify risk through effects on the epigenome and transcriptome, and new approaches to study refined phenotypes for a greater appreciation of the developmental and genetic causes of NTDs. PMID:32423763 | PMC:PMC7321880 | DOI:10.1016/j.tins.2020.04.009

BMC Med Genomics. 2020 May 13;13(1):68. doi: 10.1186/s12920-020-0714-1. ABSTRACT BACKGROUND: The causes for thousands of individually rare recessive diseases have been discovered since the adoption of next generation sequencing (NGS). Following the molecular diagnosis in older children in a family, parents could use this information to opt for fetal genotyping in subsequent pregnancies, which could inform decisions about elective termination of pregnancy. The use of NGS diagnostic sequencing in families has not been demonstrated to yield benefit in subsequent pregnancies to reduce recurrence. Here we evaluated whether genetic diagnosis in older children in families supports reduction in recurrence of recessive neurogenetic disease. METHODS: Retrospective study involving families with a child with a recessive pediatric brain disease (rPBD) that underwent NGS-based molecular diagnosis. Prenatal molecular testing was offered to couples in which a molecular diagnosis was made, to help couples seeking to prevent recurrence. With this information, families made decisions about elective termination. Pregnancies that were carried to term were assessed for the health of child and mother, and compared with historic recurrence risk of recessive disease. RESULTS: Between 2010 and 2016, 1172 families presented with a child a likely rPBD, 526 families received a molecular diagnosis, 91 families returned to the clinic with 101 subsequent pregnancies, and 84 opted for fetal genotyping. Sixty tested negative for recurrence for the biallelic mutation in the fetus, and all, except for one spontaneous abortion, carried to term, and were unaffected at follow-up. Of 24 that genotyped positive for the biallelic mutation, 16 were electively terminated, and 8 were carried to term and showed features of disease similar to that of the older affected sibling(s). Among the 101 pregnancies, disease recurrence in living offspring deviated from the expected 25% to the observed 12% ([95% CI 0·04 to 0·20], p = 0·011). CONCLUSIONS: Molecular diagnosis in an older child, coupled with prenatal fetal genotyping in subsequent pregnancies and genetic counselling, allows families to make informed decisions to reduce recessive neurogenetic disease recurrence. PMID:32404165 | PMC:PMC7218834 | DOI:10.1186/s12920-020-0714-1

Brain. 2020 Apr 1;143(4):e31. doi: 10.1093/brain/awaa070. NO ABSTRACT PMID:32227164 | PMC:PMC7174030 | DOI:10.1093/brain/awaa070

Am J Hum Genet. 2020 Apr 2;106(4):484-495. doi: 10.1016/j.ajhg.2020.03.001. Epub 2020 Mar 26. ABSTRACT Glycosylphosphatidylinositol (GPI)-anchored proteins are critical for embryogenesis, neurogenesis, and cell signaling. Variants in several genes participating in GPI biosynthesis and processing lead to decreased cell surface presence of GPI-anchored proteins (GPI-APs) and cause inherited GPI deficiency disorders (IGDs). In this report, we describe 12 individuals from nine unrelated families with 10 different bi-allelic PIGK variants. PIGK encodes a component of the GPI transamidase complex, which attaches the GPI anchor to proteins. Clinical features found in most individuals include global developmental delay and/or intellectual disability, hypotonia, cerebellar ataxia, cerebellar atrophy, and facial dysmorphisms. The majority of the individuals have epilepsy. Two individuals have slightly decreased levels of serum alkaline phosphatase, while eight do not. Flow cytometric analysis of blood and fibroblasts from affected individuals showed decreased cell surface presence of GPI-APs. The overexpression of wild-type (WT) PIGK in fibroblasts rescued the levels of cell surface GPI-APs. In a knockout cell line, transfection with WT PIGK also rescued the GPI-AP levels, but transfection with the two tested mutant variants did not. Our study not only expands the clinical and known genetic spectrum of IGDs, but it also expands the genetic differential diagnosis for cerebellar atrophy. Given the fact that cerebellar atrophy is seen in other IGDs, flow cytometry for GPI-APs should be considered in the work-ups of individuals presenting this feature. PMID:32220290 | PMC:PMC7118585 | DOI:10.1016/j.ajhg.2020.03.001

Parkinsonism Relat Disord. 2019 Nov;68:8-16. doi: 10.1016/j.parkreldis.2019.09.015. Epub 2019 Sep 28.

ABSTRACT

Cerebellar ataxia is a hallmark of coenzyme Q₁₀ (CoQ₁₀) deficiency associated with COQ8A mutations. We present four patients, one with novel COQ8A pathogenic variants all with early, prominent handwriting impairment, dystonia and only mild ataxia. To better define the phenotypic spectrum and course of COQ8A disease, we review the clinical presentation and evolution in 47 reported cases. Individuals with COQ8A mutation display great clinical variability and unpredictable responses to CoQ₁₀ supplementation. Onset is typically during infancy or childhood with ataxic features associated with developmental delay or regression. When disease onset is later in life, first symptoms can include: incoordination, epilepsy, tremor, and deterioration of writing. The natural history is characterized by a progression to a multisystem brain disease dominated by ataxia, with disease severity inversely correlated with age at onset. Six previously reported cases share with ours, a clinical phenotype characterized by slowly progressive or static writing difficulties, focal dystonia, and speech disorder, with only minimal ataxia. The combination of writing difficulty, dystonia and ataxia is a distinctive constellation that is reminiscent of a previously described clinical entity called Dystonia Ataxia Syndrome (DYTCA) and is an important clinical indicator of COQ8A mutations, even when ataxia is mild or absent.

PMID:31621627 | DOI:10.1016/j.parkreldis.2019.09.015

Ann Clin Transl Neurol. 2018 Jul 17;5(8):996-1010. doi: 10.1002/acn3.597. eCollection 2018 Aug.

ABSTRACT

Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis-characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.

PMID:30128325 | PMC:PMC6093839 | DOI:10.1002/acn3.597