Recent Advances in the Genetics of Ataxias: An Update on Novel Autosomal Dominant Repeat Expansions.

Purpose Of Review: Autosomal dominant cerebellar ataxias, also known as spinocerebellar ataxias (SCAs), are genetically and clinically diverse neurodegenerative disorders characterized by progressive cerebellar dysfunction. Despite advances in sequencing technologies, a large proportion of patients with SCA still lack a definitive genetic diagnosis. The advent of advanced bioinformatic tools and emerging genomics technologies, such as long-read sequencing, offers an unparalleled opportunity to close the diagnostic gap for hereditary ataxias.

The GAA repeat expansion is a major cause of ataxia in the Cypriot population.

Dominantly inherited intronic GAA repeat expansions in the fibroblast growth factor 14 gene have recently been shown to cause spinocerebellar ataxia 27B. Currently, the pathogenic threshold of (GAA) repeat units is considered highly penetrant, while (GAA) is likely pathogenic with reduced penetrance. This study investigated the frequency of the GAA repeat expansion and the phenotypic profile in a Cypriot cohort with unresolved late-onset cerebellar ataxia.

The First Case of Autosomal Recessive Cerebellar Ataxia with Prominent Paroxysmal Non-kinesigenic Dyskinesia Caused by a Truncating FGF14 Variant in a Turkish Patient.

Background: ATX-FGF/SCA27A has been exclusively associated with heterozygous variants in the FGF14 gene, presenting with postural tremor, slowly progressive cerebellar ataxia, and psychiatric and behavioral disturbances.

Objectives: This study describes the first case of ATX-FGF/SCA27A linked to a biallelic frameshift variant in the FGF14 gene.

Methods: Whole-exome sequencing (WES) was conducted using the Illumina NovaSeq 6000 platform, and the identified variant was confirmed using Sanger sequencing.

Evaluation of National Academies of Sciences, Engineering, and Medicine (NASEM, 2021) feed evaluation model on predictions of milk protein yield on Québec commercial dairy farms.

A recent study assessed the ability of 4 feed evaluation models to predict milk protein yield (MPY) in a commercial context, with data of 541 cows from 23 dairy herds in the province of Québec, Canada. However, the recently published Nutrient Requirements of Dairy Cattle from the National Academies of Sciences, Engineering, and Medicine (NASEM, 2021) was not released at that time. Thus, the current study evaluated NASEM using the same dataset.

A comprehensive integration of factors affecting vitamin B concentration in milk of Holstein cows: Genetic variability, milk productivity, animal characteristics, and feeding management.

Daily vitamin B (VB) requirements of humans can naturally be fulfilled by animal product consumption, especially products from ruminants because of bacteria dwelling in their rumen. Indeed, only bacteria can synthesize this vitamin. Milk is hence an excellent source of VB.

Screening for SCA27B, CANVAS and other repeat expansion disorders in Greek patients with late-onset cerebellar ataxia suggests a need to update current diagnostic algorithms.

Objective: Late-onset cerebellar ataxia (LOCA) is a slowly progressive cerebellar disorder with symptom onset ≥30years of age. Intronic tandem repeat expansions (TREs) in RFC1 and FGF14 have recently emerged as common causes of LOCA. The relative contribution of classic vs.

Clinical, Radiological and Pathological Features of a Large American Cohort of Spinocerebellar Ataxia (SCA27B).

Objectives: Spinocerebellar ataxia 27B due to GAA repeat expansions in the fibroblast growth factor 14 (FGF14) gene has recently been recognized as a common cause of late-onset hereditary cerebellar ataxia. Here we present the first report of this disease in the US population, characterizing its clinical manifestations, disease progression, pathological abnormalities, and response to 4-aminopyridine in a cohort of 102 patients bearing GAA repeat expansions.

Methods: We compiled a series of patients with SCA27B, recruited from 5 academic centers across the United States.

Effects of protein and forage source on performance and splanchnic and mammary net fluxes of nutrients in lactating dairy cows.

This study was conducted to determine if the decreased MP supply predicted by the NRC (2001) when canola meal (CM) substitutes soybean meal (SBM) was supported by direct measurement of net portal absorption of AA or energy-yielding nutrients, plus the effect of the type of forage in CM-based rations. Nine Holstein cows with indwelling catheters in splanchnic blood vessels, 8 also with a ruminal cannula, were used to examine the effects of protein source in corn silage-based diets, comparing SBM versus CM, and forage source in CM-based diets, comparing corn versus grass silage. The cows were allocated to a triple 3 × 3 Latin square design with 21-d periods.

Neurological disorders caused by novel non-coding repeat expansions: clinical features and differential diagnosis.

Nucleotide repeat expansions in the human genome are a well-known cause of neurological disease. In the past decade, advances in DNA sequencing technologies have led to a better understanding of the role of non-coding DNA, that is, the DNA that is not transcribed into proteins. These techniques have also enabled the identification of pathogenic non-coding repeat expansions that cause neurological disorders.

A Case of Non-ketotic Hyperglycemic Hemichorea and Fahr Syndrome.

Non-ketotic hyperglycemic hemichorea (NHH) denotes acute hemichorea or hemiballism in patients with poorly controlled diabetes with striatal abnormalities seen on brain MRI. Here, we describe a case with diabetes mellitus and primary hypoparathyroidism who developed NHH with bilateral chorea due to the abrupt stopping of her diabetic regimen. She presented with subacute and progressive bilateral asymmetric chorea.

Spinocerebellar ataxia 27B (SCA27B), a frequent late-onset cerebellar ataxia.

Genetic cerebellar ataxias are still a diagnostic challenge, and yet not all of them have been identified. Very recently, in early 2023, a new cause of late-onset cerebellar ataxia (LOCA) was identified, spinocerebellar ataxia 27B (SCA27B). This is an autosomal dominant ataxia due to a GAA expansion in intron 1 of the FGF14 gene.

The genetic landscape and phenotypic spectrum of GAA-FGF14 ataxia in China: a large cohort study.

Background: An intronic GAA repeat expansion in FGF14 was recently identified as a cause of GAA-FGF14 ataxia. We aimed to characterise the frequency and phenotypic profile of GAA-FGF14 ataxia in a large Chinese ataxia cohort.

Methods: A total of 1216 patients that included 399 typical late-onset cerebellar ataxia (LOCA), 290 early-onset cerebellar ataxia (EOCA), and 527 multiple system atrophy with predominant cerebellar ataxia (MSA-c) were enrolled.

GAA-FGF14 disease: defining its frequency, molecular basis, and 4-aminopyridine response in a large downbeat nystagmus cohort.

Background: GAA-FGF14 disease/spinocerebellar ataxia 27B is a recently described neurodegenerative disease caused by (GAA) expansions in the fibroblast growth factor 14 (FGF14) gene, but its phenotypic spectrum, pathogenic threshold, and evidence-based treatability remain to be established. We report on the frequency of FGF14 (GAA) and (GAA) expansions in a large cohort of patients with idiopathic downbeat nystagmus (DBN) and their response to 4-aminopyridine.

Methods: Retrospective cohort study of 170 patients with idiopathic DBN, comprising in-depth phenotyping and assessment of 4-aminopyridine treatment response, including re-analysis of placebo-controlled video-oculography treatment response data from a previous randomised double-blind 4-aminopyridine trial.

Neuroradiological findings in GAA- ataxia (SCA27B): more than cerebellar atrophy.

Background: GAA- ataxia (SCA27B) is a recently reported late-onset ataxia caused by a GAA repeat expansion in intron 1 of the gene. Initial studies revealed cerebellar atrophy in 74-97% of patients. A more detailed brain imaging characterization of GAA- ataxia is now needed to provide supportive diagnostic features and earlier disease recognition.

RFC1 repeat expansions in downbeat nystagmus syndromes: frequency and phenotypic profile.

Objectives: The cause of downbeat nystagmus (DBN) remains unknown in a substantial number of patients ("idiopathic"), although intronic GAA expansions in FGF14 have recently been shown to account for almost 50% of yet idiopathic cases. Here, we hypothesized that biallelic RFC1 expansions may also represent a recurrent cause of DBN syndrome.

Methods: We genotyped the RFC1 repeat and performed in-depth phenotyping in 203 patients with DBN, including 65 patients with idiopathic DBN, 102 patients carrying an FGF14 GAA expansion, and 36 patients with presumed secondary DBN.

Spinocerebellar ataxia 27B: A novel, frequent and potentially treatable ataxia.

Hereditary ataxias, especially when presenting sporadically in adulthood, present a particular diagnostic challenge owing to their great clinical and genetic heterogeneity. Currently, up to 75% of such patients remain without a genetic diagnosis. In an era of emerging disease-modifying gene-stratified therapies, the identification of causative alleles has become increasingly important.