De novo FRMD5 Missense Variants in Patients with Childhood-Onset Ataxia, Prominent Nystagmus, and Seizures.

BACKGROUND: FRMD5 variants were recently identified in patients with developmental delay, ataxia, and eye movement abnormalities. OBJECTIVES: We describe 2 patients presenting with childhood-onset ataxia, nystagmus, and seizures carrying pathogenic de novo FRMD5 variants. Weighted gene co-expression network analysis (WGCNA) was performed to gain insights into the function of FRMD5 in the brain. METHODS: Trio-based whole-exome sequencing was performed in both patients, and CoExp web tool was used to conduct WGCNA. RESULTS: Both patients presented with developmental delay, childhood-onset ataxia, nystagmus, and seizures. Previously unreported findings were diffuse choreoathetosis and dystonia of the hands (patient 1) and areas of abnormal magnetic resonance imaging signal in the white matter (patient 2). WGCNA showed that FRMD5 belongs to gene networks involved in neurodevelopment and oligodendrocyte function. CONCLUSIONS: We expanded the phenotype of FRMD5-related disease and shed light on its role in brain function and development. We recommend including FRMD5 in the genetic workup of childhood-onset ataxia and nystagmus. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Exploring genetic counselors' practice of discussing clinical trials with patients.

Despite concerted and accelerated efforts to increase the knowledge of medicine and disease via clinical studies, clinical trials continue to face low enrollment for all patient groups. The dissemination of the availability of clinical trials to individuals with or at risk for hereditary disorders is critical. This study acts as a foundation in determining an unexplored role of clinical trial discussion in genetic counseling practice. Board-certified, patient-facing genetic counselors in the United States were invited to participate in an anonymous survey via the National Society of Genetic Counselors. Between February and April 2022, 157 participants (N = 157) completed the survey on clinical trial discussion with patients, barriers, and facilitators to discussing clinical trials with patients, research experience, and demographics. Survey results identified that most respondents have discussed the availability of clinical trials with a patient (85%). Almost one-third have previous research experience working for a clinical trial (30%). Most agreed that discussions of clinical trials are within the scope of genetic counseling (82%); however, one-third were not comfortable discussing them with patients (34%). Respondents who know how to find specific clinical trials (p < 0.001) were reportedly more likely to be comfortable discussing clinical trials with their patients. In addition to clinical research exposure, this study suggests that further education and training is necessary for genetic counselors to learn how to find and identify specific clinical trials for their patients. In turn, we hope for this to increase genetic counselors' comfort of clinical trial discussion.

Expanding the spectrum of KCNJ6-related disorders: Milder phenotype with pathological startle responses.

Keppen-Lubinsky syndrome is caused by pathogenic variants in KCNJ6, which encodes the inwardly rectifying channel subfamily J6. The four confirmed cases reported to date were characterized by severe intellectual disability, global developmental delay, feeding difficulties, and dysmorphic features. All but one of the cases also had a severe form of lipodystrophy, resulting in tightly adherent facial skin and appearance of premature aging. Here, we describe a 36-year-old female with a de novo pathogenic variant in KCNJ6 (NM_002240.5: c.460G>T; p.(Gly154Cys)) presenting with mild intellectual disability, subtle dysmorphic features, obsessive-compulsive disorder, and an exaggerated startle response. This case indicates that KCNJ6-related disorders should be considered in patients with less pronounced dysmorphic features and milder cognitive impairment, as well as in patients with startle disorders.

mTORC1 functional assay reveals SZT2 loss-of-function variants and a founder in-frame deletion.

Biallelic pathogenic variants in SZT2 result in a neurodevelopmental disorder with shared features, including early-onset epilepsy, developmental delay, macrocephaly, and corpus callosum abnormalities. SZT2 is as a critical scaffolding protein in the amino acid sensing arm of the mTORC1 signalling pathway. Due to its large size (3432 amino acids), lack of crystal structure, and absence of functional domains, it is difficult to determine the pathogenicity of SZT2 missense and in-frame deletions, but these variants are increasingly detected and reported by clinical genetic testing in individuals with epilepsy. To exemplify this latter point, here we describe a cohort of 12 individuals with biallelic SZT2 variants and phenotypic overlap with SZT2-related neurodevelopmental disorders. However, the majority of individuals carried one or more SZT2 variants of uncertain significance (VUS), highlighting the need for functional characterization to determine, which, if any, of these VUS were pathogenic. Thus, we developed a novel individualized platform to identify SZT2 loss-of-function variants in the context of mTORC1 signalling and reclassify VUS. Using this platform, we identified a recurrent in-frame deletion (SZT2 p.Val1984del) which was determined to be a loss-of-function variant and therefore likely pathogenic. Haplotype analysis revealed that this single in-frame deletion is a founder variant in those of Ashkenazi Jewish ancestry. Moreover, this approach allowed us to tentatively reclassify all of the VUS in our cohort of 12 individuals, identifying five individuals with biallelic pathogenic or likely pathogenic variants. Clinical features of these five individuals consisted of early-onset seizures (median 24 months), focal seizures, developmental delay and macrocephaly similar to previous reports. However, we also show a widening of the phenotypic spectrum, as none of the five individuals had corpus callosum abnormalities, in contrast to previous reports. Overall, we present a rapid assay to resolve VUS in SZT2, identify a founder variant in individuals of Ashkenazi Jewish ancestry, and demonstrate that corpus callosum abnormalities is not a hallmark feature of this condition. Our approach is widely applicable to other mTORopathies including the most common causes of the focal genetic epilepsies, DEPDC5, TSC1/2, MTOR and NPRL2/3.

CACNA1H variants are not a cause of monogenic epilepsy.

CACNA1H genetic variants were originally reported in a childhood absence epilepsy cohort. Subsequently, genetic testing for CACNA1H became available and is currently offered by commercial laboratories. However, the current status of CACNA1H as a monogenic cause of epilepsy is controversial, highlighted by ClinGen's recent reclassification of CACNA1H as disputed. We analyzed published CACNA1H variants and those reported in ClinVar and found none would be classified as pathogenic or likely pathogenic per the American College of Medical Genetics classification criteria. Moreover, Cacna1h did not modify survival in a Dravet Syndrome mouse model. We observed a mild increase in susceptibility to hyperthermia-induced seizures in mice with reduced Cacna1h expression. Overall, we conclude that there is limited evidence that CACNA1H is a monogenic cause of epilepsy in humans and that this gene should be removed from commercial genetic testing panels to reduce the burden of variants of uncertain significance for healthcare providers, families and patients with epilepsy.

Novel bi-allelic FBXO7 variants in a family with early-onset typical Parkinson's disease.

Bi-allelic mutations in FBXO7 are classically associated with a complex phenotype, known as parkinsonian-pyramidal syndrome. We describe two brothers affected by typical early onset Parkinson's disease (EOPD), who carry novel compound heterozygous variants in FBXO7. Our report highlights that typical EOPD can be part of an expanding FBXO7-related phenotype.

Novel THAP1 missense variant with incomplete penetrance in a case of generalized young onset dystonia showing good response to deep brain stimulation.

We describe a case of young onset generalized dystonia, harboring a previously unreported likely pathogenic THAP1 missense variant (c.109 G > A; p.Glu37Lys) that was inherited from her unaffected father. Moreover, we report a positive effect of deep brain stimulation, particularly on the cervical component of dystonia.

The Impact of Family History on the Clinical Features of Huntington's Disease.

BACKGROUND: Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder. In most cases the disease is inherited from a parent, although a considerable number of affected persons have no reported family history of the disease. While CAG repeat length is negatively correlated with age of symptom onset, variability exists suggesting that other variables may influence symptom onset. OBJECTIVES: The objective of this study is to determine whether awareness of a family history of HD has an impact on symptom onset and disease manifestations. METHODS: Data were obtained from Enroll-HD to compare subjects with a family history of HD to subjects without on various key clinical outcomes. In addition, multiple regressions were performed to investigate the impact of family history on the age at onset of depression and motor symptoms. RESULTS: 4,285 mutation positive subjects were included in the analysis, of which 4.81% had a negative family history. Controlling for CAG repeat length, a positive family history predicted an onset of depression 11.438 years earlier and an onset of motor symptoms 6.681 years earlier when compared to having a negative family history. Subjects with a positive family history were more likely to report behavioral manifestations as the initial major symptom of HD (38.6% vs. 29.6%, p = 0.023), and were more likely to report previous suicidal ideation/attempts (26.2% vs. 20.3%, p = 0.046). CONCLUSIONS: A positive family history of HD appears to be associated with an earlier onset of depression and overall disease manifestations. Implications regarding the role of genetic versus environmental contributions to symptom onset in HD are discussed.

Reproductive decision-making among individuals at risk for familial amyotrophic lateral sclerosis.

This qualitative study explored the reproductive decision-making process in individuals at 50% risk for familial amyotrophic lateral sclerosis (FALS) from families with a known genetic mutation. We spoke with 10 individuals utilizing a semi-structured interview. Participants had a first-degree relative with FALS, made reproductive decisions in the past 30 years and did not know their genetic status during decision-making. We delineated themes emerging in individuals who chose to have children, those who chose not to have children, and themes describing the process in general. Results showed that those who chose to have children believed that regardless of disease, life is productive. They compared ALS relatively favorably to other diseases, always planned on having children, and hoped for a cure. Individuals who chose not to have children had extensive experience with ALS and caretaking, saw ALS as an inevitable tragedy, and avoided serious relationships. In consultation with partners, individuals considered other reproductive options. Conversations varied in length, and often strengthened relationships. Children experiencing death of a parent was a primary concern. In conclusion, the reproductive decision-making process is complex. Results can guide future research and provide direction for healthcare professionals when discussing the family planning process and prior to predictive genetic testing.