Analysis of ASPM in an ethnically diverse cohort of 400 patient samples: perspectives of the molecular diagnostic laboratory

Primary Autosomal Recessive Microcephaly (MCPH) is characterized by congenital microcephaly usually without additional clinical findings. The most common gene implicated in MCPH is ASPM and a large percentage of mutations described have been homozygous and in consanguineous families primarily of East Asian and Middle Eastern origin. ASPM sequencing was performed on 400 patients between the years 2009 and 2012. Seventy of the patient samples were also analyzed for copy number changes in the ASPM gene. Forty protein truncating mutations, including 29 novel mutations, were identified in 39 patients with MCPH. Approximately one third of patients were compound heterozygotes, indicative of non‐consanguinity in these patients. In addition, 46 non‐synonymous variants were identified and interpreted as variants of uncertain significance. No deletion/duplication in ASPM was identified in the patients analyzed. A wide ethnic distribution was observed, including the first reported patients with ASPM‐related MCPH of Hispanic descent. Clinical information was collected for 26 of the ASPM‐positive patients and 41 of the ASPM‐negative patients. As more individuals are identified with MCPH, we anticipate that we will continue to identify ASPM mutation‐positive patients from all ethnic origins supporting the occurrence of this genetic condition beyond that of consanguineous families of certain ethnic populations.     

Whole exome sequencing unravels disease‐causing genes in consanguineous families in Qatar

Whole exome sequencing (WES) has greatly facilitated the identification of causal mutations for diverse human genetic disorders. We applied WES as a molecular diagnostic tool to identify disease‐causing genes in consanguineous families in Qatar. Seventeen consanguineous families with diverse disorders were recruited. Initial mutation screening of known genes related to the clinical diagnoses did not reveal the causative mutations. Using WES approach, we identified the definitive disease‐causing mutations in four families: (i) a novel nonsense homozygous (c.1034C>G) in PHKG2 causing glycogen storage disease type 9C (GSD9C) in a male with initial diagnosis of GSD3; (ii) a novel homozygous 1‐bp deletion (c.915del) in NSUN2 in a male proband with Noonan‐like syndrome; (iii) a homozygous SNV (c.1598C>G) in exon 11 of IDUA causing Hurler syndrome in a female proband with unknown clinical diagnosis; (iv) a de novo known splicing mutation (c.1645+1G>A) in PHEX in a female proband with initial diagnosis of autosomal recessive hypophosphatemic rickets. Applying WES as a diagnostic tool led to the unambiguous identification of disease‐causing mutations in phenotypically complex disorders or correction of the initial clinical diagnosis in ?25% of our cases.     

胎儿常染色体隐性遗传性多囊肾的MRI表现(附10例分析)

目的：探讨胎儿双侧常染色体隐性遗传性多囊肾（ARPKD）的MRI表现及其诊断价值。方法：对10例经超声和病理证实的胎儿双侧ARPKD的MRI影像资料进行回顾性分析。结果：①8例双肾体积明显均匀增大,但肾外形保持;②T2WI上,1例双肾信号呈中等以上增高,均匀一致;8例双肾皮髓质内见弥漫性针尖大小信号增高的囊泡影,呈放射状排列,笔者称为＂苦瓜样＂改变,1例信号正常;③羊水无法显示5例,羊水极少5例;④8例未见膀胱显示;⑤合并9种畸形,其中前脑无裂畸形1例,脑积水2例,Dandy-Walker综合征2例,枕部脑膜膨出2例,颅内出血并孔洞脑1例,肺发育不良5例,多发性肝囊肿1例,唇裂1例,Meckel-Gruber综合征1例。结论：ARPKD的MRI表现具有特异性,且不受羊水量和胎儿体位的影响,可作为产前超声检查的重要补充手段,并提高其合并畸形的检出率。     

家族性常染色体隐性遗传早发性帕金森综合征ATP13A2基因突变研究

目的 探讨常染色体隐性遗传早发性帕金森综合征(autosomal recessive early-onset parkinsonism,AREP)家系患者中ATP13A2基因的突变特点.方法 应用聚合酶链反应结合DNA直接序列分析方法对25个已排除Parkin,DJ-1和PINK1基因纯合突变及复合杂合突变的AREP家系共46例患者进行ATP13A2基因突变分析.结果 AREP患者中未发现ATP13A2基因的致病突变,发现了6个已知多态,为IVS6+70A>G、IVS12+66A>G、m1849C>T、IVS20-56 G>A、m2671C>T和m2824G>A.结论 家族性AREP患者中ATP13A2基因的突变可能罕见.     

三个常染色体隐性遗传性青少年型帕金森综合征家系的基因型与表型分析

目的探讨常染色体隐性遗传性青少年型帕金森综合征(autosomal recessive juvenile parkinson-ism,AR-JP)parkin基因的突变及临床特征。方法应用聚合酶链反应、DNA测序和限制性核酸内切酶酶切等技术对15个AR-JP家系先证者的parkin基因进行突变研究。结果发现3个家系有parkin基因的突变,其中2个家系含parkin基因的杂合缺失突变,分别为第2外显子的202-203delAG及第9外显子的1069-1074delGTGTCC;另一家系发现一个杂合点突变,为第12外显子的1422(T→C)。其中1069-1074delGTGTCC和1422(T→C)为新的突变。3个家系共6名患者,发病年龄18~31岁,平均25.2±5.7岁;病情进展慢,腱反射活跃或亢进、症状波动常见;对小剂量多巴制剂反应良好。结论我国的AR-JP家系存在parkin基因的突变;含parkin基因突变的AR-JP患者有帕金森病的一般临床表现,又有其独特的临床特征。     

Purine nucleoside phosphorylase deficiency: a new case report and identification of two novel mutations (Gly156A1a and Val217Ile), only one of which (Gly156A1a) is deleterious

Purine nucleoside phosphorylase (PNP) deficiency results in an autosomal recessive immunodeficiency disease characterized by initial involvement of cellular immunity and neurological manifestations with subsequent abnormalities of humoral immunity. The initial presentation and clinical course has varied widely in the relatively few published cases. The molecular basis has been reported in only 10 patients, precluding evaluation of phenotype-genotype relationships. We now report clinical, immunologic, and molecular findings in a new case of relatively early onset that emphasizes hypotonia and developmental delay as early manifestations. The patient carried two novel missense mutations (Gly56A1a and Val217Ile) on the same allele in apparent homozygosity. Expression of each of the mutant enzymes in vitro demonstrated that the Gly156A1a mutation abolished enzyme activity while the Val217Ile mutation was without obvious effect and is therefore a normal variant. Such "normal" polymorphisms might be associated with a variable response to the immunosuppressive PNP inhibitors currently in clinical trials.     

Auditory canal atresia,humeroscapular synostosis,and other skeletal abnormalities: Confirmation of the autosomal recessive “SAMS” syndrome

A second girl with the unique combination of auditory canal atresia and scapulohumeral synostosis is reported. This patient also had bilateral clubfeet and genital abnormalities. The other patient reported with this syndrome and the presently reported child both had consanguineous parents. Mental development was normal in both children. The acronym SAMS (Short stature, Auditory canal atresia, Mandibular hypoplasia, and Skeletal abnormalities) was suggested to describe the main manifestations in this syndrome. © 2002 Wiley‐Liss, Inc.     

Assessment of the genetic causes of recessive childhood non-syndromic deafness in the UK - implications for genetic testing

Approximately one in 2000 children is born with a genetic hearing impairment, mostly inherited as a non-syndromic, autosomal recessive trait, for which more than 30 different genes have been identified. Previous studies have shown that one of these genes, connexin 26 (GJB2), accounts for 30-60% of such deafness, but the relative contribution of the many other genes is not known, especially in the outbred UK population. This lack of knowledge hampers the development of diagnostic genetic services for deafness. In an effort to determine the molecular aetiology of deafness in the population, 142 sib pairs with early-onset, non-syndromic hearing impairment were recruited. Those in whom deafness could not be attributed to GJB2 mutations were investigated further for other mapped genes. The genetic basis of 55 cases (38.7%) was established, 33.1% being due to mutations in the GJB2 gene and 3.5% due to mutations in SLC26A4. None of the remaining 26 loci investigated made a significant contribution to deafness in a Caucasian population. We suggest that screening the GJB2 and SLC26A4 genes should form the basis of any genetic testing programme for childhood deafness and highlight a number of important issues for consideration and future work.