Large French-Canadian family with Lewy body parkinsonism: exclusion of known loci.

The identification of rare, large families with Parkinson's disease (PD) has provided important clues that have contributed to our understanding of this complex disorder. We have identified a large French-Canadian kindred that spans five generations consisting of more than 90 individuals. A total of 65 individuals now have been examined, had venous blood drawn, and DNA extracted. Two-point and multipoint linkage analysis was performed to assess linkage to known PD genes or loci. Within the third and fourth generations of this family there are 10 living, plus 3 deceased members with well-documented levodopa responsive parkinsonism. Autopsy results on 1 member demonstrated the loss of pigmented neurons in the substantia nigra and the presence of alpha-synuclein positive Lewy bodies. Four of the PD patients have prominent postural and kinetic tremors that preceded their parkinsonism by up to 10 years. Two other individuals within the family have prominent isolated postural and kinetic tremors without parkinsonism. The alpha-synuclein(4q21.3-23), Parkin(6q25.2-27), PARK3 (2p13), PARK4, and ubiquitin carboxy terminal hydrolase-L1 (4p14-16.3) and PARK6 and PARK7 (1p35-36) loci were excluded in this kindred using closely linked markers. The clinical and pathological features of this family are consistent with the diagnosis of PD. This family further demonstrates the known genetic heterogeneity in PD and is large enough that a genome-wide screen has been undertaken in an effort to identify a novel PD gene.     

Functional alteration of PARL contributes to mitochondrial dysregulation in Parkinson's disease

Molecular genetics has linked mitochondrial dysfunction to the pathogenesis of Parkinson's disease by the discovery of rare, inherited mutations in gene products that associate with the mitochondria. Mutations in PTEN-induced kinase-1 (PINK1), which encodes a mitochondrial kinase, and PARKIN, encoding an E3 ubiquitin ligase, are the most frequent causes of recessive Parkinson's disease. Recent functional studies have revealed that PINK1 recruits PARKIN to mitochondria to initiate mitophagy, an important autophagic quality control mechanism that rids the cell of damaged mitochondria. PINK1 is post-translationally processed into a cleaved form whose levels are tightly regulated, although the significance of this processing is unknown. Here we demonstrate that the mitochondrial protease presenilin-associated rhomboid-like (PARL) can affect the proteolytic processing of PINK1 and that normal PINK1 localization and stability requires PARL's catalytic activity. PARL deficiency impairs PARKIN recruitment to mitochondria, suggesting PINK1's processing and localization are important in determining its interaction with PARKIN. We sequenced the PARL gene in Parkinson's disease patients and discovered a novel missense mutation in a functional domain of PARL's N-terminus. This PARL mutant is not sufficient to rescue PARKIN recruitment, suggesting that impaired mitophagy may be an underlying mechanism of disease pathogenesis in patients with PARL mutations.     

Large deletions account for an increasing number of mutations in SGCE

Myoclonus‐dystonia (M‐D) (MIM 159900) is a rare “dystonia plus” syndrome, characterized by rapid myoclonic jerks, predominantly in the neck and upper limbs, in combination with dystonia. Mutations in the gene ε‐sarcoglycan (SGCE) are known to be responsible for approximately one‐third of cases. We screened 21 probands diagnosed with M‐D for large deletions who were mutation negative as determined by PCR‐direct sequencing. Multiplex PCR and quantification of PCR products was performed using a modified application of denaturing high performance liquid chromatography (dHPLC). We have identified two novel large multiexonic deletions of SGCE, which were confirmed by amplifying and sequencing the deletion breakpoints. Five other families were found to harbor small mutations identified by direct sequencing. Analysis of the region surrounding the deletions demonstrates that both deletions are the result of nonhomologous recombination with homologous end joining. This is only the second report of intragenic deletions with SGCE and it highlights the need to include exonic copy number variation when performing mutational analysis of SGCE. © 2007 Movement Disorder Society     

全身性癫癎伴高热惊厥附加症致病基因的连锁定位研究

目的　定位全身性癫癎伴高热惊厥附加症的致病基因。方法　采用全基因组扫描的连锁分析方法对全身性癫癎伴高热惊厥附加症4个家系进行研究。结果　在染色体5q34多点连锁分析显示最大LOD值为3. 815。染色体单体型分析将连锁范围缩小至D5S820至D5S1476之间4. 0厘摩(cM)的区域。结论　全身性癫癎伴高热惊厥附加症致病基因定位在染色体5q34。     

Two novel disease-causing variants in BMPR1B are associated with brachydactyly type A1

Brachydactyly type A1 is an autosomal dominant disorder primarily characterized by hypoplasia/aplasia of the middle phalanges of digits 2–5. Human and mouse genetic perturbations in the BMP-SMAD signaling pathway have been associated with many brachymesophalangies, including BDA1, as causative mutations in IHH and GDF5 have been previously identified. GDF5 interacts directly as the preferred ligand for the BMP type-1 receptor BMPR1B and is important for both chondrogenesis and digit formation. We report pathogenic variants in BMPR1B that are associated with complex BDA1. A c.975A>C (p.(Lys325Asn)) was identified in the first patient displaying absent middle phalanges and shortened distal phalanges of the toes in addition to the significant shortening of middle phalanges in digits 2, 3 and 5 of the hands. The second patient displayed a combination of brachydactyly and arachnodactyly. The sequencing of BMPR1B in this individual revealed a novel c.447-1G>A at a canonical acceptor splice site of exon 8, which is predicted to create a novel acceptor site, thus leading to a translational reading frameshift. Both mutations are most likely to act in a dominant-negative manner, similar to the effects observed in BMPR1B mutations that cause BDA2. These findings demonstrate that BMPR1B is another gene involved with the pathogenesis of BDA1 and illustrates the continuum of phenotypes between BDA1 and BDA2.     

Translated mutation in the Nurr1 gene as a cause for Parkinson's disease.

Multiple genes have been now identified as causing Parkinson's disease (PD). In 2003, two mutations were identified in exon 1 of the Nurr1 gene in 10 of 107 individuals with familial PD. To date, investigators have only focused on screening for these known mutations of the Nurr1 gene. All individuals were recruited from two Parkinson's disease clinics in Canada. Following PCR amplification of each exon of the Nurr1 gene, samples underwent denaturing high-performance liquid chromatography (DHPLC) analysis. Ten individuals also underwent direct sequencing as well as any samples where variants were identified. The Nurr1 gene was evaluated for 202 PD individuals, 37% of whom had at least one relative with PD and 100 control non-PD individuals. Using DHPLC and direct sequencing, we did not detect any sequence variants in exon 1. Variants in amplicon 6 were seen and direct sequencing confirmed a known NI6P polymorphism in intron 6. Novel polymorphisms were also identified in exon 3 and intron 5. A novel mutation was identified in exon 3 in one nonfamilial PD individual. This heterozygous C-to-G transversion resulted in a serine-to-cysteine substitution and was not identified in any of the other 602 chromosomes screened. Mutations in the Nurr1 gene in our large cohort of familial and sporadic PD individuals are rare. The novel mutation in exon 3 is predicted to affect phosphorylation and functional studies to assess this are underway. This is the first coding mutation identified in the Nurr1 gene for Parkinson's disease.     

Refinement of the DYT15 locus in myoclonus dystonia.

Inherited myoclonus dystonia (MD) is an autosomal dominant disorder in which we previously mapped a novel locus to chromosome18p11 (OMIM number: 607488). Since no further informative STS markers were found within the flanking shared regions, we utilized single nucleotide polymorphisms (SNP) for fine-mapping. All known or predicted genes within this region were directly sequenced. We identified three recombinant SNPs in the distal region but none from the proximal region. Our previous linked region has now been reduced to 3.18 Mb but direct sequencing of all seven known and four predicted genes with EST support did not identify any mutations..     

Brachydactyly A-1 mutations restricted to the central region of the N-terminal active fragment of Indian Hedgehog

Mutations in the gene Indian Hedgehog (IHH) that cause Brachydactyly A-1 (BDA1) have been restricted to a specific region of the N-terminal active fragment of Indian Hedgehog involving codons 95, 100, 131, and 154. We describe two novel mutations in codons 128 and 130, not previously implicated in BDA1. Furthermore, we identified an independent mutation at codon 131 and we also describe a New Zealand family, which carries the ‘Farabee'' founder mutation and haplotype. All of the BDA1 mutations occur in a restricted area of the N-terminal active fragment of the IHH and are in contrast to those mutations causing an autosomal recessive acrocapitofemoral dysplasia, whose mutations are located at the distal N- and C-terminal regions of IHH-N and are physically separated from the BDA1-causing mutations. The identification of multiple independent mutations in codons 95, 100, and now in 131, implicate a discrete function for this region of the protein. Finally, we present a clinical review of all reported and confirmed cases of BDA1, highlighting features of the disorder, which add to the spectrum of the IHH mutations.     

全面性癫癎伴高热惊厥附加症基因定位及GABRA6基因测序研究

目的　对全面癫伴高热惊厥附加症 (GEFS )家系进行基因定位 ,并对候选基因进行测序研究。方法　用连锁分析的方法对GEFS 家系进行研究 ;设计GABRA6外显子 内含子交界处全部 9对内含子引物 ,采用Sanger双脱氧链终止法 ,对GABRA6PCR测序。 结果　在 5 q34区域最大LOD值 3.815。GABRA6基因测序显示外显子 8有一C/G多态性。结论　GEFS 症致病基因在 5 q34区域取得了肯定的连锁关系。在该研究的两家系未发现GABRA6基因突变 ;所显示的单个碱基多态性对其他癫家系的连锁分析及其他癫综合征分子遗传学机制的研究均有意义     

全身性癫癎伴热性惊厥附加症2个家系致病基因GABRG2测序分析

目的:对全身癫癎伴热性惊厥附加症(GEFS )2个家系候选基因GABRG2进行测序研究.方法:设计GABRG2外显子-内含子交界处全部9对内含子引物,采用Sanger双脱氧链终止法,对GABRG2 PCR测序.结果:2个家系未发现GABRG2基因突变,GABRG2基因测序显示外显子5的第13密码子有一C/T多态性.结论:本研究结果所显示的单个碱基多态性对其他癫癎家系的连锁分析及其他癫癎综合征分子遗传机制的研究有重要意义.