Cerebellar ataxia (CA) and hereditary spastic paraplegia (HSP) are two of the most prevalent motor disorders with extensive locus and allelic heterogeneity. We implemented clinical exome sequencing, ...followed by filtering data for a 'movement disorders' gene panel, as a generic test to increase variant detection in 76 patients with these disorders. Segregation analysis or phenotypic re-evaluation was utilized to substantiate findings. Disease-causing variants were identified in 9 of 28 CA patients, and 8 of 48 HSP patients. In addition, possibly disease-causing variants were identified in 1 and 8 of the remaining CA and HSP patients, respectively. In 10 patients with CA, the total disease-causing or possibly disease-causing variants were detected in 8 different genes, whereas 16 HSP patients had such variants in 12 different genes. In the majority of cases, the identified variants were compatible with the patient phenotype. Interestingly, in some patients variants were identified in genes hitherto related to other movement disorders, such as TH variants in two siblings with HSP. In addition, rare disorders were uncovered, for example, a second case of HSP caused by a VCP variant. For some patients, exome sequencing results had implications for treatment, exemplified by the favorable L-DOPA treatment in a patient with HSP due to ATP13A2 variants (Parkinson type 9). Thus, clinical exome sequencing in this cohort of CA and HSP patients suggests broadening of disease spectra, revealed novel gene-disease associations, and uncovered unanticipated rare disorders. In addition, clinical exome sequencing results have shown their value in guiding practical patient management.
A 35-year-old woman underwent bilateral lung transplantation for primary ciliary dyskinesia and developed vascular tumors over a slow time course. Initial presentation of non-specific vascular tumors ...in the lungs and liver for up to 6 years after transplantation evolved toward bilateral ovarian angiosarcoma. Tumor analysis by haplotyping and human leukocyte antigen typing showed mixed donor chimerism, proving donor origin of the tumoral lesions. In retrospect, the donor became brain dead following neurosurgical complications for a previously biopsy-proven cerebral hemangioma, which is believed to have been a precursor lesion of the vascular malignancy in the recipient. Donor-transmitted tumors should always be suspected in solid organ transplant recipients in case of uncommon disease course or histology, and proper tissue-based diagnosis using sensitive techniques should be pursued.
Multiple pterygium syndromes (MPS) comprise a group of multiple congenital anomaly disorders characterized by webbing (pterygia) of the neck, elbows, and/or knees and joint contractures ...(arthrogryposis). MPS are phenotypically and genetically heterogeneous but are traditionally divided into prenatally lethal and nonlethal (Escobar) types. Previously, we and others reported that recessive mutations in the embryonal acetylcholine receptor g subunit (
CHRNG) can cause both lethal and nonlethal MPS, thus demonstrating that pterygia resulted from fetal akinesia. We hypothesized that mutations in acetylcholine receptor-related genes might also result in a MPS/fetal akinesia phenotype and so we analyzed 15 cases of lethal MPS/fetal akinesia without
CHRNG mutations for mutations in the
CHRNA1,
CHRNB1,
CHRND, and rapsyn (
RAPSN) genes. No
CHRNA1,
CHRNB1, or
CHRND mutations were detected, but a homozygous
RAPSN frameshift mutation, c.1177-1178delAA, was identified in a family with three children affected with lethal fetal akinesia sequence. Previously,
RAPSN mutations have been reported in congenital myasthenia. Functional studies were consistent with the hypothesis that whereas incomplete loss of rapsyn function may cause congenital myasthenia, more severe loss of function can result in a lethal fetal akinesia phenotype.
Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS: MIM 270550) is a neurodegenerative disorder characterized by early-onset cerebellar ataxia with spasticity and peripheral ...neuropathy. This disorder, considered to be rare, was first described in the late seventies among French Canadians in the isolated Charlevoix-Saguenay region of Quebec. Nowadays, it is known that the disorder is not only limited to this region but occurs worldwide. Our objective was to identify cases of autosomal recessive spastic ataxia of
C
harlevoix-
S
aguenay (ARSACS) in Dutch patients with recessive early-onset cerebellar ataxia by sequencing the complete
SACS
gene. In a Dutch cohort of 43 index patients with ataxia onset before age 25, we identified 16 index patients (total 23 patients) with mutations in the
SACS
gene. Nine of them had homozygous mutations, and seven of them had compound heterozygous mutations. Retrospectively, the phenotype of patients carrying mutations was remarkably uniform: cerebellar ataxia with onset before age 13 years, lower limb spasticity and sensorimotor axonal neuropathy, and cerebellar (vermis) atrophy on magnetic resonance imaging, consistent with the core ARSACS phenotype previously described. The high rate of mutations (37%) identified in this cohort of Dutch patients suggests that ARSACS is substantially more frequent than previously estimated. We predict that the availability of
SACS
mutation analysis as well as an increasing awareness of the characteristic ARSACS phenotype will lead to the diagnosis of many additional patients, possibly even at a younger age.
ABSTRACT
The advent of massive parallel sequencing is rapidly changing the strategies employed for the genetic diagnosis and research of rare diseases that involve a large number of genes. So far it ...is not clear whether these approaches perform significantly better than conventional single gene testing as requested by clinicians. The current yield of this traditional diagnostic approach depends on a complex of factors that include gene‐specific phenotype traits, and the relative frequency of the involvement of specific genes. To gauge the impact of the paradigm shift that is occurring in molecular diagnostics, we assessed traditional Sanger‐based sequencing (in 2011) and exome sequencing followed by targeted bioinformatics analysis (in 2012) for five different conditions that are highly heterogeneous, and for which our center provides molecular diagnosis. We find that exome sequencing has a much higher diagnostic yield than Sanger sequencing for deafness, blindness, mitochondrial disease, and movement disorders. For microsatellite‐stable colorectal cancer, this was low under both strategies. Even if all genes that could have been ordered by physicians had been tested, the larger number of genes captured by the exome would still have led to a clearly superior diagnostic yield at a fraction of the cost.
In order to determine the impact of exome sequencing in molecular diagnostics, the diagnostic yields for traditional Sanger‐based sequencing and exome sequencing followed by targeted bioinformatics analysis were compared for five genetically heterogeneous disorders. We find that exome sequencing has a much higher diagnostic rate than Sanger sequencing for four of these, being deafness, blindness, mitochondrial disease, and movement disorders. We conclude that exome sequencing is applicable to a broad range of heterogeneous genetic diseases, being an overall effective choice, with respect to both diagnostic yield as well as costs.
The predominantly autosomal dominant disorder, oculodentodigital dysplasia (ODDD) has high penetrance with intra- and interfamilial phenotypic variability. Abnormalities observed in ODDD affect the ...eye, dentition, and digits of the hands and feet. Patients present with a characteristic facial appearance, narrow nose, and hypoplastic alae nasi. Neurological problems, including dysarthria, neurogenic bladder disturbances, spastic paraparesis, ataxia, anterior tibial muscle weakness, and seizures, are known to occur as well as conductive hearing loss, cardiac defects, and anomalies of the skin, hair, and nails. In 2003, our analysis of 17 ODDD families revealed that each had a different mutation within the human gap junction alpha 1 (GJA1) gene which encodes the protein connexin 43 (Cx43). Since then at least 17 publications have identified an additional 26 GJA1 mutations and in this study, we present 28 new cases with 18 novel GJA1 mutations. We include tables summarizing the 62 known GJA1 nucleotide changes leading to Cx43 protein alterations and the phenotypic information available on 177 affected individuals from 54 genotyped families. Mutations resulting in ODDD occur in each of the nine domains of the Cx43 protein, and we review our functional experiments and those in the literature, examining the effects of 13 different Cx43 mutations upon gap junction activity. Hum Mutat 0, 1-10, 2009.
PDF
