Multipoint linkage mapping of the Emery-Dreifuss muscular dystrophy gene.

The clinical features to establish the diagnosis of X-linked Emery-Dreifuss muscular dystrophy (EMD) were recently redefined at the European EMD workshop in Baarn 1991. These criteria were used to select families from the literature and two new families for linkage analysis with the DNA markers F9, DX52, DXS15, F8C and DXS115. Recombinations are observed with the DNA markers F9, DXS52 and DXS15. No recombinations were found with F8C and DXS115. Multipoint linkage analysis indicates with a maximum location score of 73.9 that the EMD locus maps very close to F8C.     

X-linked centronuclear myopathy: mapping the gene to Xq28.

The X-linked recessive centronuclear/myotubular myopathy (XLR-CNM/MTM1), a severe neonatal disorder characterized by generalized hypotonia, muscle weakness and primary asphyxia, has recently been mapped to Xq28. This report presents linkage analysis data of eight families with X-linked centronuclear myopathy. Four probes from the region Xq26-27 and five Xq28 probes were used to get more precise gene localization and marker order. St14 (DXS52), fully informative in all families, shows significant linkage to the CNM gene (z = 3.60; theta = 0.05), followed by DX13 (DXS15) (z = 2.03; theta = 0.06) and F8 (z = 1.86; theta = 0.00). Combination of the physical map derived by Kenwrick and Gitschier (1989) and our linkage data lead to the most probable order R/GCP-G6PD-(XLR-CNM-F8)-p767-St14-cpX67-++ +DX13 placing the CNM gene close to F8. The results of this study confirm strong linkage of the CNM gene to the region Xq28 and will permit carrier testing and prenatal diagnosis in CNM families. We conclude that the precise localization of this devastating disorder may be of great importance for genetic counselling in families at risk. The lack of information about gene frequency and mutation rate as well as the severity and burden of the disease point to the inevitable need for accurate clinical diagnosis.     

X-chromosome markers and manic-depressive illness. Rejection of linkage to Xq28 in nine bipolar pedigrees

Numerous reports have been published concerning linkage of X-chromosome markers of the q28 region (including protan and deutan color blindness [CB] and glucose-6-phosphate dehydrogenase deficiency) to manic-depressive illness. We studied nine bipolar pedigrees (in which there was no male-to-male transmission) in an attempt to detect linkage, using three tightly linked polymorphic DNA loci, DXS15, DXS52 and F8C (factor 8 gene), all of which are closely linked to the CB and glucose 6-phosphate dehydrogenase classic Xq28 markers. Linkage to this region of Xq28 could be excluded unequivocally in these nine families. When these data were combined with our earlier series of bipolar pedigrees, informative for either protan or deutan CB, a total of 14 bipolar pedigrees have been studied, with no evidence of linkage or heterogeneity. At a recombination fraction (theta) of 1%, this series had greater than 95% power to detect linkage if only 50% of the pedigrees studied were linked to the CB region. Our failure to confirm the previously reported linkage of manic-depressive illness to the CB region of the X chromosome indicates that this linkage is not as common as previously suggested.     

Linkage analyses between dominant X-linked Charcot-Marie-Tooth disease, and 15 Xq11–Xq21 microsatellites in a new large family: Three new markers are closely linked to the gene

X-linked dominant inheritance was suspected in a large family with Charcot-Marie-Tooth disease since no male to male transmission was observed, and since the sensory and motor neuropathy was more severe in males than in females. To test linkage to the dominant X-linked Charcot-Marie-Tooth disease (DCMTX) locus in Xq13, genotypes of 19 affected and 19 unaffected individuals from this family were determined for 4 microsatellite markers. Close linkage to mfd66 (DXS453) was found by bipoint analysis (Zmax = 4.8 at θ = 0.00). Multipoint analysis mapped the gene between the androgen receptor and DXYS1. In addition, linkage analysis performed with 11 microsatellite markers, derived from a high density map spanning 16 cM on Xq11–Xq21 revealed 3 new tightly linked loci: afm287zgl (DXS1216), afm261zh5 and afm207zg5 (DXS995). Multipoint analysis localized the DCMTX gene to a 7.5 cM interval between afm123xd4 (DXS988) and afm116xg1 (DXS986). Combined analysis with these new microsatellites provides a powerful tool for carrier detection because of their high informativity and the small genetic distance (< 10 cM) between the markers flanking the gene.     

一条人脑胶质瘤相关新基因的克隆与表达

目的运用基因芯片技术获取正常成人脑组织与人脑胶质瘤中差异表达的基因，并对其中一条与脑胶质瘤相关的新基因进行了克隆和表达的研究。方法抽提正常成人脑组织与人脑胶质瘤组织中的mRNA来制备探针，经杂交、洗涤后，通过计算机观察二者表达谱的差异情况，对681F05克隆子进行了Northern blot，生物信息学分析和蛋白质的表达。结果通过四次基因芯片筛选，获得15条与胶质瘤相关的新基因，经northern blot证实681F05基因在人正常脑组织中低表达，而在人脑胶质瘤中高表达。BLASTn和BLASTx分析显示，它们编码蛋白与线虫Cyp-10蛋白同源性分别为52％和72％。cDNA序列分析发现这两个克隆是同一个基因[命名为cyclophilin—like gene（PPIL3）]的两个不同的剪切体（PPIL3a和PPIL3b）。并在大肠杆菌中得到了PPIL3a和PPIL3b与GST较好表达的融合蛋白。结论基因芯片筛选正常脑组织与人脑胶质瘤差异表达的基因具有样品用量少，高质量，高速度，高敏感等特性。681F05基因可能是与人脑胶质瘤形成有关的一条全长新基因。     

脑胶质瘤相关的全长新基因PPIL-3的克隆和蛋白质特性的研究

目的 运用基因芯片技术获取正常成人脑组织与人脑胶质瘤中差异表达的基因,并对其中一条与脑胶质瘤相关的新基因进行了克隆和表达的研究.方法 抽提正常成人脑组织与人脑胶质瘤组织中的mRNA来制备探针,经杂交、洗涤后,通过计算机观察二者表达谱的差异情况,对681F05克隆子进行了Northern blot,生物信息学分析和蛋白质的表达.结果 通过4次基因芯片筛选,获得15条与胶质瘤相关的新基因,经Northern blot证实681F05基因在人正常脑组织中低表达,而在人脑胶质瘤中高表达.BLASTn和BLASTx分析显示,它们编码蛋白与线虫Cyp-10蛋白同源性分别为52%和72%.cDNA序列分析发现这两个克隆是同一个基因(cyclophilin-like gene,PPIL3)的两个不同的剪切体(PPIL3a和PPIL3b).并在大肠杆菌中得到了PPIL3a和PPIL3b与GST较好表达的融合蛋白.PPIL3b蛋白具有依赖于Ca2+/Mg2+核酸酶活性,其核酸酶活性可被一定浓度的K+/Na+抑制.结论 基因芯片筛选正常脑组织与人脑胶质瘤差异表达的基因具有样品用量少、高质量、高速度、高敏感等特性.681F05基因可能是与人脑胶质瘤形成有关的一条全长新基因.     

Genetic control of sensitivity to hippocampal cell death induced by kainic acid: a quantitative trait loci analysis

Host genetic factors are likely to contribute to differences in individual susceptibility to seizure-induced excitotoxic neuronal damage. Similarly, inbred strains of mice differ in their susceptibility to the kainic acid (KA) model of seizure-induced cell death, but the genes responsible for the differences are not known. Here, we define the inheritance patterns of susceptibility to KA-induced neurodegeneration in the hippocampus by assessing 331 back-cross (N2) progeny of two inbred mouse strains, C57BL/6 and FVB/N, previously shown to display resistance and sensitivity to KA-induced cell death, respectively. Results of phenotypic analysis suggest that the difference in susceptibility between these two strains is conferred by a single dominant gene. Therefore, we used an N2 back-cross between the inbred C57BL/6 and FVB/N strains for a genome-wide search for quantitative trait loci (QTLs), which are chromosomal sites containing genes influencing the magnitude of susceptibility. Genome-wide interval mapping in N2 progeny identified a locus on distal chromosome (Chr) 18 with a peak LOD score of 4.9 localized between D18Mit186 and D18Mit4 as having the strongest and most significant effect in this model. QTLs of minor effect were detected on Chr 15 (D15Mit174-D15Mit156) and Chr 4 (D4Mit264-D4Mit91), with peak LOD scores of 3.02 and 2.46, respectively. The three significant QTLs (Chrs 4, 15, 18) together account for nearly 25% of the trait variance for both genders combined. Reduced KA-induced cell death susceptibility was observed in a congenic strain in which the highly susceptible FVB/N strain carried putative resistance alleles from the C57BL/6 strain on Chr 18.     

Exome sequencing identifies KIAA1377 and C5orf42 as susceptibility genes for monomelic amyotrophy

Precise topographic localization, predominance in males mostly of Asian origin, and existence of some familial cases suggest a genetic background for monomelic amyotrophy. To identify susceptibility genes for monomelic amyotrophy, we performed whole-exome sequencing of four unrelated patients with monomelic amyotrophy and detected a total of 45 novel nonsynonymous single-nucleotide polymorphisms as unique variants to monomelic amyotrophy compared to control exomes. Genetic association analysis showed significant association with monomelic amyotrophy in the Gly668Ser variant of the KIAA1377 gene (odds ratio=4.62, P-value=0.0040) and the Pro1794Leu variant of the C5orf42 gene (odds ratio=4.63, P-value=0.0040). Moreover, the combination of two variants increased the risk of monomelic amyotrophy (P=1.4×10(-5), OR=61.69, 95% confidence interval=9.62-394.94, in case of combination of two heterozygotes). These data suggest that KIAA1377 and C5orf42 synergistically play a role as susceptibility genes for monomelic amyotrophy.     

Dense linkage disequilibrium mapping in the 15q11-q13 maternal expression domain yields evidence for association in autism

Autism [MIM 209850] is a neurodevelopmental disorder exhibiting a complex genetic etiology with clinical and locus heterogeneity. Chromosome 15q11-q13 has been proposed to harbor a gene for autism susceptibility based on (1) maternal-specific chromosomal duplications seen in autism and (2) positive evidence for linkage disequilibrium (LD) at 15q markers in chromosomally normal autism families. To investigate and localize a potential susceptibility variant, we developed a dense single nucleotide polymorphism (SNP) map of the maternal expression domain in proximal 15q. We analyzed 29 SNPs spanning the two known imprinted, maternally expressed genes in the interval (UBE3A and ATP10C) and putative imprinting control regions. With a marker coverage of 1/10 kb in coding regions and 1/15 kb in large 5' introns, this map was employed to thoroughly dissect LD in autism families. Two SNPs within ATP10C demonstrated evidence for preferential allelic transmission to affected offspring. The signal detected at these SNPs was stronger in singleton families, and an adjacent SNP demonstrated transmission distortion in this subset. All SNPs showing allelic association lie within islands of sequence homology between human and mouse genomes that may be part of an ancestral haplotype containing a functional susceptibility allele. The region was further explored for recombination hot spots and haplotype blocks to evaluate haplotype transmission. Five haplotype blocks were defined within this region. One haplotype within ATP10C displayed suggestive evidence for preferential transmission. Interpretation of these data will require replication across data sets, evaluation of potential functional effects of associated alleles, and a thorough assessment of haplotype transmission within ATP10C and neighboring genes. Nevertheless, these findings are consistent with the presence of an autism susceptibility locus in 15q11-q13.     

Linkage of DNA markers at Xq28 to adrenoleukodystrophy and adrenomyeloneuropathy present within the same family

We present a large kindred that contained patients with either adrenoleukodystrophy (ALD) or adrenomyeloneuropathy (AMN). The pedigree clearly supported the X-linked mode of inheritance of the nonneonatal form of ALD/AMN. Analysis with DNA markers at Xq28 suggested segregation of both ALD and AMN with an identical haplotype. This indicated that nonneonatal ALD and AMN are caused by a mutation in the same gene at Xq28. It showed, furthermore, that phenotypic differences between ALD and AMN are not necessarily the consequence of allelic heterogeneity due to different mutations within the same gene. The maximal lod score for linkage of the ALD/AMN gene and the multiallelic anonymous DNA marker at DXS52 was 3.0 at a recombination fraction of 0.00. This made a prenatal or presymptomatic diagnosis and heterozygote detection by DNA analysis with this marker reliable.     

Genetic localization of a new locus for recessive familial spastic paraparesis to 15q13-15.

OBJECTIVE: To characterize a new gene locus for familial spastic paraparesis (FSP). BACKGROUND: FSP is a genetically heterogeneous group of upper motor neuron syndromes. It can be inherited as an autosomal dominant, autosomal recessive, or X-linked disorder. Four loci for autosomal dominant FSP have been genetically mapped, and two genes have been shown responsible for the X-linked type. In addition, two loci for autosomal recessive type have been reported and mapped to chromosomes 8q and 16q. The gene for the 16q locus has been characterized as a mitochondrial protein. METHODS: Eight recessive FSP families from America and Europe were used for genetic linkage analysis. The known recessive loci (8q and 16q) and the X-linked loci (PLP and L1CAM genes) were screened through PCR amplification, followed by linkage analysis, single-strand conformational polymorphism, or both. RESULTS: All the families except one revealed lack of linkage to the known loci for recessive and X-linked types of FSP. One of the eight families showed data consistent with linkage to the previously characterized 8q locus. Analysis of all the families for possible linkage to other candidate loci revealed significant positive lod scores for markers in chromosome 15q. The maximum multipoint combined lod score for the non-8q families was Z = 3.14 for markers D15S1007, D15S971, D15S118, and D15S1012, at a distance of 6.41 cM from the marker D15S1007, in between D15S971 and D15S118. CONCLUSIONS: Our data suggest a new locus for recessive FSP linked to chromosome 15q, and that this may be the most common one.     

Effects of temperature and fatigue on the electromechanical delay components

Introduction: Neuromuscular activation can be influenced by both muscle temperature (Tm) and fatigue. Methods: To assess the effects of Tm and fatigue on the electromechanical delay (EMD), 15 participants performed voluntary isometric contractions of different intensities under neutral (Tm_N), low (Tm_L), and high (Tm_H) Tm, before and after a fatiguing exercise. During contraction, electromyogram (EMG), mechanomyogram (MMG), and force (F) were recorded from the biceps brachii muscle. The EMD and the latencies between EMG and MMG (Δt EMG‐MMG, which includes the electrochemical processes of EMD) and between MMG and F (Δt MMG‐F, which includes the mechanical processes of EMD) were calculated. Results: Tm_L increased only Δt EMG‐MMG, both before and after fatigue. Fatigue lengthened EMD, Δt EMG‐MMG, and Δt MMG‐F under all Tm to a similar extent. Conclusions: While fatigue increased all EMD components, muscle cooling affected only the electrochemical but not the mechanical processes of EMD. Muscle Nerve, 2013     

The gene for X-linked myotubular myopathy is located in an 8 Mb region at the border of Xq27.3 and Xq28

X-linked recessive myotubular myopathy (XLMTM) is a rare and severe neonatal neuromuscular disease characterized by muscle weakness, hypotonia, and respiratory problems. Here we report an extensive linkage analysis in two families with XLMTM. Using 18 markers in the Xq27-Xqter region we found a maximum two-point lod score of Z = 4.00 at Θ = 0.00 for the marker II-10 (DXS466). Three recombinations were detected between markers and the disease locus. At the distal side of Xq27.3 a recombination was present in between RNI (DXS369) and VK23b (DXS297), another in between VK23b (DXS297) and II-10 (DXS466), and at the proximal side of Xq28 a recombination in between U6.2 (DXS304) and Cpx67 (DXS134). Combining the results of both families we conclude that XLMTM is located in the 8 Mb (11 cM) region between VK23b (DXS297) and Cpx67 (DXS134).     

Evidence of a founder haplotype refines the X-linked Charcot–Marie-Tooth (CMTX3) locus to a 2.5 Mb region

X-linked Charcot-Marie-Tooth (CMTX) disease is a common inherited degenerative disorder of the peripheral nerve. Previously, our laboratory identified a large New Zealand/United Kingdom (NZ/UK) family mapping to the CMTX3 locus (Xq26.3-27.1). We have now identified a second large, Australian X-linked CMT family that links to the CMTX3 locus. This new family has the same phenotype as our previously described CMTX3 family, with slightly milder disease in males than CMTX1 and asymptomatic carrier females. This study also includes the re-analysis of one of the original US pedigrees reporting the CMTX3 locus. The large Australian family shared the complete disease haplotype with our original NZ/UK family, while the American family shared only the distal portion of the disease haplotype. Comparison of the frequency of the CMTX3 haplotype to the normal population showed strong statistical evidence (p < 0.0001) indicating that the smaller shared haplotype is identical by descent. This suggests that the new CMTX3 family, our previously reported family, and the original American CMTX3 family have a common ancestor, and the disease in these families is caused by a founder mutation. The ancestral recombination observed in the American family refines the CMTX3 interval to a 2.5 Mb region between DXS984 and DXS8106. In this region, 11 out of the 15 annotated genes have been excluded for pathogenic mutations.     

Functional polymorphisms of the cytochrome P450 1A2 (CYP1A2) gene and prolonged QTc interval in schizophrenia

CYP1A2 is an important inducible enzyme involved in the metabolism of antipsychotics. This study examined two functional polymorphisms in the gene as potential markers in predicting prolongation of QTc interval in patients treated with antipsychotics. QT intervals were measured by 12-lead electrocardiography (ECG) for patients with a DSM-IV diagnosis of schizophrenia. Genomic DNA extracted from venous blood were genotyped for the two polymorphisms by PCR-RFLP. Statistically significant result for CYP1A2(*)1F was noted for all patients receiving chlorpromazine equivalent doses of above 300 mg and also for a further subgroup on antipsychotics known to be CYP1A2 substrates (p=0.007, mean QTc in ms for A/A: 395.5+/-15.1, A/C: 425.7+/-25.1, C/C: 427.3+/-20.7). For CYP1A2(*)1C, there was no statistically significant association between genotypes and mean QTc interval. Overall, there was a trend of those with the C allele of the CYP1A2(*)1F polymorphism having longer QTc intervals. The results of this study suggest that the CYP1A2(*)1F polymorphism may contribute to the risk of developing prolonged QT-interval in patients who are treated with higher doses of antipsychotics.     

Combined use of DNA probes in first-trimester prenatal diagnosis of hemophilia A

First-trimester prenatal diagnoses of hemophilia A were heretofore obtained by using either intragenic factor VIII markers or linked extragenic polymorphic markers. Postulating that the combined use of all the available intragenic and extragenic markers can render such diagnoses more frequently feasible and more reliable, we carried out ten first-trimester prenatal diagnoses in male fetuses at risk for hemophilia A by DNA analysis of chorionic villus employing in combination the intragenic Bcl I polymorphism and the St 14 (DXS 52) or DX 13 (DXS 15) extragenic probes. A diagnosis of hemophilia was obtained in three fetuses, with a diagnosis of normal fetus obtained in the remaining seven. Seven diagnoses are confirmed by factor VIII assays carried out at the time of abortion, in the mid-trimester or at birth. A factor VIII probe recognizing Bcl I polymorphism was useful in 4 of 6 diagnoses; St 14, in 5 of 6; and DX 13 in 3 of 5. In two cases, St 14 was the only useful probe for diagnosis. Even though no recombination between extragenic probes and factor VIII gene was detected in this study, when only extragenic markers were informative we advised diagnostic confirmation on fetal plasma obtained by fetoscopy. Hence, first-trimester prenatal diagnosis of hemophilia A is feasible for the great majority of fetuses at risk through combined use of all the available intragenic and extragenic probes, providing key family members are available.     

Effects of neuromuscular fatigue on electromechanical delay of the leg extensors and flexors in young men and women

Introduction: We examined the effects of neuromuscular fatigue on volitional electromechanical delay (EMD) of leg extensors and flexors between genders. Methods: Twenty‐one men and 20 women performed 2 maximal voluntary contractions (MVCs), followed by intermittent isometric contractions of leg extensors and flexors using a 0.6 duty cycle (6‐s contraction, 4‐s relaxation) at 50% of MVC until volitional fatigue was achieved. MVCs were again performed at 0, 7, 15, and 30 min post‐fatigue. Results: EMD was greater compared with baseline at all post‐fatigue time phases for the leg flexors (P = 0.001–0.007), while EMD was greater at Post0, Post15 and Post30 (P = 0.001–0.023) for the leg extensors. EMD was also greater for leg extensors compared with leg flexors only at Post0. Conclusion: No differential gender‐related fatigue effects on EMD were shown. There were different fatigue‐induced responses between leg extensors and flexors, with leg extensors exhibiting higher EMD immediately post‐fatigue. Muscle Nerve 52 : 844–851, 2015     

X-linked nonprogressive congenital cerebellar hypoplasia: Clinical description and mapping to chromosome Xq

We examined a large family in which an X-linked recessive congenital ataxia manifested in 7 males from three generations. The affected boys first exhibited a marked delay of early developmental motor milestones. A neurological syndrome became evident by 5 to 7 years of age and included cerebellar ataxia, dysarthria, and external ophthalmoplegia; there were no symptoms of mental retardation, spastic paraparesis, or sensory loss. Neuroimaging studies revealed hypoplasia of cerebellar hemispheres and vermis. The disease showed no progression beyond early childhood. The unique heredity and clinical features clearly distinguish this new entity from a variety of previously described familial ataxias. Pairwise linkage analysis and haplotype reconstruction allowed us to map the gene responsible for this disorder to a 38-cM interval on chromosome Xp11.21-q24 flanked by the loci DXS991 and DXS1001. Upon multipoint linkage analysis, the disease gene was determined to be located most likely in the proximal part of chromosome Xq, with the maximal lod score of 4.66 at the locus DXS1059 (Xq23). This is the first example of the genetic mapping of a pure congenital cerebellar hypoplasia syndrome.     

人脑胶质瘤相关的二条全长新基因报导及染色体定位

目的 报导与人脑胶质瘤相关的二条新基因及其在染色体上的定位。方法 对发现的脑胶质瘤相关的二条新基因进行测序，Northern blot和序列局部对比查询（BLAST）分析，同时运用染色体辐射杂交（RH）技术对其进行染色体定位。结果 这二条新基因都是全长新基因，基因库登录号分别为AF225513和AF329277。经Northern blot证实436F11基因在人正常脑组织中高表达,而在人脑胶质瘤中低表达，而另一条基因507 E08则相反。RH染色体定位显示436F11基因在6q21-q23的D6S304和D62S2156 Marker之间，507E08基因在D14S1066Marker和D14S265 Marker之间。结论 找到了二条与人脑胶质瘤相关的全长新基因及其在染色体上的相应定位，这为胶质瘤的基因治疗提供了新思路。