Breakpoint mapping of 13 large parkin deletions/duplications reveals an exon 4 deletion and an exon 7 duplication as founder mutations

Early-onset Parkinson’s disease (EOPD) has been associated with recessive mutations in parkin (PARK2). About half of the mutations found in parkin are genomic rearrangements, i.e., large deletions or duplications. Although many different rearrangements have been found in parkin before, the exact breakpoints involving these rearrangements are rarely mapped. In the present study, the exact breakpoints of 13 different parkin deletions/duplications, detected in 13 patients out of a total screened sample of 116 EOPD patients using Multiple Ligation Probe Amplification (MLPA) analysis, were mapped using real time quantitative polymerase chain reaction (PCR), long-range PCR and sequence analysis. Deletion/duplication-specific PCR tests were developed as a rapid and low cost tool to confirm MLPA results and to test family members or patients with similar parkin deletions/duplications. Besides several different deletions, an exon 3 deletion, an exon 4 deletion and an exon 7 duplication were found in multiple families. Haplotype analysis in four families showed that a common haplotype of 1.2 Mb could be distinguished for the exon 7 duplication and a common haplotype of 6.3 Mb for the deletion of exon 4. These findings suggest common founder effects for distinct large rearrangements in parkin

Translational models for vascular cognitive impairment: a review including larger species.

BACKGROUND: Disease models are useful for prospective studies of pathology, identification of molecular and cellular mechanisms, pre-clinical testing of interventions, and validation of clinical biomarkers. Here, we review animal models relevant to vascular cognitive impairment (VCI). A synopsis of each model was initially presented by expert practitioners. Synopses were refined by the authors, and subsequently by the scientific committee of a recent conference (International Conference on Vascular Dementia 2015). Only peer-reviewed sources were cited. METHODS: We included models that mimic VCI-related brain lesions (white matter hypoperfusion injury, focal ischaemia, cerebral amyloid angiopathy) or reproduce VCI risk factors (old age, hypertension, hyperhomocysteinemia, high-salt/high-fat diet) or reproduce genetic causes of VCI (CADASIL-causing Notch3 mutations). CONCLUSIONS: We concluded that (1) translational models may reflect a VCI-relevant pathological process, while not fully replicating a human disease spectrum; (2) rodent models of VCI are limited by paucity of white matter; and (3) further translational models, and improved cognitive testing instruments, are required

Peters Plus syndrome is a new congenital disorder of glycosylation and involves defective Omicron-glycosylation of thrombospondin type 1 repeats

Peters Plus syndrome is an autosomal recessive disorder characterized by anterior eye chamber defects, disproportionate short stature, developmental delay, and cleft lip and/or palate. It is caused by splice site mutations in what was thought to be a beta1,3-galactosyltransferase-like gene (B3GALTL). Recently, we and others found this gene to encode a beta1,3-glucosyltransferase involved in the synthesis of the disaccharide Glc-beta1,3-Fuc-Omicron-that occurs on thrombospondin type 1 repeats of many biologically important proteins. No functional tests have been performed to date on the presumed glycosylation defect in Peters Plus syndrome. We have established a sensitive immunopurification-mass spectrometry method, using multiple reaction monitoring, to analyze Omicron-fucosyl glycans. It was used to compare the reporter protein properdin from Peters Plus patients with that from control heterozygous relatives. In properdin from patients, we could not detect the Glc-beta1,3-Fuc-Omicron-disaccharide, and we only found Fuc-Omicron-at all four Omicron-fucosylation sites. In contrast, properdin from heterozygous relatives and a healthy volunteer carried the Glc-beta1,3-Fuc-Omicron-disaccharide. These data firmly establish Peters Plus syndrome as a new congenital disorder of glycosylatio

A homozygous deletion of a normal variation locus in a patient with hearing loss from non-consanguineous parents

International audienceInternational databases with information on copy number variation of the human genome are an important reference for laboratories using high resolution whole genome screening. Genomic deletions or duplications which have been detected in the healthy population and thus marked as normal copy number variants (CNVs) can be filtered out using these databases when searching for pathogenic copy number changes in patients. However, a potential pitfall of this strategy is that reported normal CNVs often do not elicit further investigation, and thus may remain unrecognized when they are present in a (pathogenic) homozygous state. The impact on disease of CNVs in the homozygous state may thus remain undetected and underestimated

Peters Plus Syndrome Is Caused by Mutations in B3GALTL, a Putative Glycosyltransferase

Peters Plus syndrome is an autosomal recessive disorder characterized by anterior eye-chamber abnormalities, disproportionate short stature, and developmental delay. After detection of a microdeletion by array-based comparative genomic hybridization, we identified biallelic truncating mutations in the β1,3-galactosyltransferase–like gene (B3GALTL) in all 20 tested patients, showing that Peters Plus is a monogenic, primarily single-mutation syndrome. This finding is expected to put Peters Plus syndrome on the growing list of congenital malformation syndromes caused by glycosylation defects

Cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL)

To characterize the clinical and MRI features of 2 families with adult-onset dominant leukoencephalopathy and strokes and identify the underlying genetic cause. We applied MRI pattern recognition, whole-exome sequencing, and neuropathology. Based on brain imaging, 13 family members of 40 years or older from 2 families were diagnosed with the disease; in 11 family members of the same age, MRI was normal. In the affected family members, MRI showed a leukoencephalopathy that was disproportionately severe compared to the clinical disease. The clinical picture was dominated by ischemic and hemorrhagic strokes, slow and late cognitive deterioration, and therapy-resistant hypertension. With whole-exome sequencing, we identified one variant shared by both families and segregating with the disease: c.973C>T in CTSA. Haplotype analysis revealed a shared 1,145-kb interval encompassing the CTSA variant on chromosome 20q13.12, suggesting a common ancestor. Brain autopsy of 3 patients showed a leukoencephalopathy that was disproportionately extensive compared to the vascular abnormalities. CTSA encodes cathepsin A. Recessive CTSA mutations cause galactosialidosis. One of the numerous cathepsin A functions is to degrade endothelin-1. In the patients, striking endothelin-1 immunoreactivity was found in white matter astrocytes, correlating with increased numbers of premyelinating oligodendrocyte progenitors. This finding supports a role for endothelin-1 in the leukoencephalopathy through inhibition of oligodendrocyte progenitor maturation. CARASAL (cathepsin A-related arteriopathy with strokes and leukoencephalopathy) is a novel hereditary adult-onset cerebral small vessel disease. It is of interest that, next to the cerebral vascular abnormalities, endothelin-1 may have a role in the pathogenesis of the extensive leukoencephalopath

Naturally occurring NOTCH3 exon skipping attenuates NOTCH3 protein aggregation and disease severity in CADASIL patients

CADASIL is a vascular protein aggregation disorder caused by cysteine-altering NOTCH3 variants, leading to mid-adult-onset stroke and dementia. Here, we report individuals with a cysteine-altering NOTCH3 variant that induces exon 9 skipping, mimicking therapeutic NOTCH3 cysteine correction. The index came to our attention after a coincidental finding on a commercial screening MRI, revealing white matter hyperintensities. A heterozygous NOTCH3 c.1492G>T, p.Gly498Cys variant, was identified using a gene panel, which was also present in four first- and second-degree relatives. Although some degree of white matter hyperintensities was present on MRI in all family members with the NOTCH3 variant, the CADASIL phenotype was mild, as none had lacunes on MRI and there was no disability or cognitive impairment above the age of 60 years. RT-PCR and Sanger sequencing analysis on patient fibroblast RNA revealed that exon 9 was absent from the majority of NOTCH3 transcripts of the mutant allele, effectively excluding the mutation. NOTCH3 aggregation was assessed in skin biopsies using electron microscopy and immunohistochemistry and did not show granular osmiophilic material and only very mild NOTCH3 staining. For purposes of therapeutic translatability, we show that, in cell models, exon 9 exclusion can be obtained using antisense-mediated exon skipping and CRISPR/Cas9-mediated genome editing. In conclusion, this study provides the first in-human evidence that cysteine corrective NOTCH3 exon skipping is associated with less NOTCH3 aggregation and an attenuated phenotype, justifying further therapeutic development of NOTCH3 cysteine correction for CADASIL