A gene for arthrogryposis multiplex congenita neuropathic type is linked to D5S394 on chromosome 5qter

Research platform for children with arthrogryposis multiplex congenita: Findings from the pilot registry

A pediatric registry for arthrogryposis multiplex congenita (AMC) proposes to advance research by providing the platform to inform the distribution, etiology, and natural history of AMC. The registry was piloted on 40 families of children (mean = 8.25 years, 48% males) presenting with AMC across two hospitals in North America. Data on the child's demographic and newborn variables, mothers' and fathers' demographic variables, lifestyle habits, and medical history were collected using a telephone interview with the primary caregiver and review of medical charts. Mean gestational age was 38 weeks, 97% of children presented with lower extremity deformities, and 74% of neonatal interventions targeted the lower extremity. Newborns spent an average of 14 days in the hospital (range 2-56 days) mostly for diagnostic workup and feeding difficulties. Half (49%) of the sample had internal organ involvement. Genetic testing was done on 48% of the children, including chromosome studies, single gene, whole-exome/genome sequencing, and/or microarray studies. Genetic findings were inconclusive in most. Two-thirds of mothers (67%) reported inconsistently feeling fetal movements. This pilot study contributed to the refinement of participant selection, identification of data source, expansion of data sets, and areas for future exploration prior to the implementation of a multisite AMC pediatric registry.

Mutations in ERGIC1 cause Arthrogryposis multiplex congenita, neuropathic type

Arthrogryposis multiplex congenita (AMC) is heterogeneous group of disorders characterized by non-progressive joint contractures from birth that involve more than 1 part of the body. There are various etiologies for AMC including genetic and environmental depends on the specific type, however, for most types, the cause is not fully understood. We previously reported large Israeli Arab kindred consisting of 16 patients affected with AMC neuropathic type, and mapped the locus to a 5.5 cM interval on chromosome 5qter. Using whole exome sequencing, we have now identified homozygous pathogenic variant in the ERGIC1 gene within the previously defined linked region. ERGIC1 encodes a cycling membrane protein which has a possible role in transport between endoplasmic reticulum and Golgi. We further show that this mutation was absent in more than 200 samples of healthy unrelated individuals of the Israeli Arab population. Thus, our findings expand the spectrum of hereditary AMC and suggest that abnormalities in protein trafficking may underlie AMC-related disorders.

Lethal contractural syndrome type 3 (LCCS3) is caused by a mutation in PIP5K1C, which encodes PIPKI gamma of the phophatidylinsitol pathway

Lethal congenital contractural syndrome (LCCS) is a severe form of arthrogryposis. To date, two autosomal recessive forms of the disease (LCCS and LCCS2) have been described and mapped to chromosomes 9q34 and 12q13, respectively. We now describe a third LCCS phenotype (LCCS3)--similar to LCCS2 yet without neurogenic bladder. Using 10K single-nucleotide-polymorphism arrays, we mapped the disease-associated gene to 8.8 Mb on chromosome 19p13. Further analysis using microsatallite markers narrowed the locus to a 3.4-Mb region harboring 120 genes. Of these genes, 30 candidates were sequenced, which identified a single homozygous mutation in PIP5K1C. PIP5K1C encodes phosphatidylinositol-4-phosphate 5-kinase, type I, gamma (PIPKI gamma ), an enzyme that phophorylates phosphatidylinositol 4-phosphate to generate phosphatidylinositol-4,5-bisphosphate (PIP(2)). We demonstrate that the mutation causes substitution of aspartic acid with asparagine at amino acid 253 (D253N), abrogating the kinase activity of PIPKI gamma . Thus, a defect in the phosphatidylinositol pathway leading to a decrease in synthesis of PIP(2), a molecule active in endocytosis of synaptic vesicle proteins, culminates in lethal congenital arthrogryposis.

Arthrogryposis

Arthrogryposis is the name given to a group of musculoskeletal disorders characterized by multiple joint contractures through the body that are present at birth. There are many causes for congenital limitations of the range of motion of a joint. However, the most common form of arthrogryposis, present in 40% of cases, is a condition called amyoplasia. In many cases, abnormal nerve, muscle, and connective tissue development is involved. Hands, wrists, elbows, shoulders, hips, feet, knees, back, and jaws are affected. Because of the complexity of tissue alterations and implications in normal facial growth, the authors of this article address the aspects related to clinical manifestations and therapeutic planning for patients with this condition who seek orthodontic treatment or orthognathic surgery.

Genetics of arthrogryposis: linkage analysis approach

Arthrogryposis multiplex congenita (AMC) is a heterogeneous group of congenital contracture syndromes, some of which are hereditary. To date, four genetic loci associated with autosomal recessive arthrogryposis syndromes have been identified using the powerful tools of genome-wide linkage analysis and homozygosity mapping. In the consanguineous inbred Bedouin population in southern Israel there is an unusually high incidence of hereditary arthrogryposis. We hypothesized the high incidence of this phenotype in this specific cohort might be due to a founder effect: a mutation that occurred several generations ago, spread throughout various tribes in that population in recent generations and causes the phenotype in its homozygous form. Using linkage analysis studies, we showed the hereditary arthrogryposis in those tribes does not stem from a single genetic defect. Thus, there is genetic heterogeneity of congenital arthrogryposis in this population: the same phenotype is caused by mutations in different genes, yet to be unraveled.

Linkage mapping of the locus for inherited ovine arthrogryposis (IOA) to sheep chromosome 5

Arthrogryposis is a congenital malformation affecting the limbs of newborn animals and infants. Previous work has demonstrated that inherited ovine arthrogryposis (IOA) has an autosomal recessive mode of inheritance. Two affected homozygous recessive (art/art) Suffolk rams were used as founders for a backcross pedigree of half-sib families segregating the IOA trait. A genome scan was performed using 187 microsatellite genetic markers and all backcross animals were phenotyped at birth for the presence and severity of arthrogryposis. Pairwise LOD scores of 1.86, 1.35, and 1.32 were detected for three microsatellites, BM741, JAZ, and RM006, that are located on sheep Chr 5 (OAR5). Additional markers in the region were identified from the genetic linkage map of BTA7 and by in silico analyses of the draft bovine genome sequence, three of which were informative. Interval mapping of all autosomes produced an F value of 21.97 (p < 0.01) for a causative locus in the region of OAR5 previously flagged by pairwise linkage analysis. Inspection of the orthologous region of HSA5 highlighted a previously fine-mapped locus for human arthrogryposis multiplex congenita neurogenic type (AMCN). A survey of the HSA5 genome sequence identified plausible candidate genes for both IOA and human AMCN.

Stenotic aortic and mitral valves in three adult brothers with arthrogryposis multiplex congenita

Three brothers with arthrogryposis multiplex congenita survived into adulthood. In their fourth decade, the clinical course for each brother became complicated by severe stenoses of their aortic and mitral valves. One brother died suddenly, and the remaining 2 developed heart failure. requiring valvular replacement.

Arthrogryposis multiplex congenita (AMC), a hereditary disease in swine, maps to chromosome 5 by linkage analysis

Arthrogryposis multiplex congenita (AMC), defined as permanent joint contractures present at birth, is one of the most common congenital defects in piglets and other mammals. A genetic form of arthrogryposis was recently identified in Swiss Large White (LW) pigs. The disease is controlled by a single autosomal recessive allele designated as amc. At least 14 LW AI (artificial insemination) boars (about 25% of the Swiss population) are known to be carriers of the amc allele. A total of 219 pigs were used for linkage analysis, including seven founders (F1), three F0, 160 F2, and 49 F3 animals. All founder pigs were full or half sibs. Of the 219 pigs, 41 (18.7%) were found to be affected, while the remaining 178 (81.3%) were healthy. A comprehensive genome scan revealed that microsatellite SW1987 located on pig (Sus scrofa) Chromosome 5 (SSC5), was linked with AMC. Sixteen additional SSC5 microsatellites were selected for further genotyping to generate a multipoint map covering the AMC region. Significant pairwise linkage (LOD > 6.00) was found for AMC and eight marker loci. The order that best fit with the data was SW963-SW1987-SW152-AMC-(SW904, SW1094)-SWR1526-(SWR1974, SW310). AMC was mapped by linkage analysis to the position 92 cM, between SW152 and SW904/SW1094, which are located on SSC5 in bands q12-q23.

Homozygosity mapping of lethal congenital contractural syndrome type 2 (LCCS2) to a 6 cM interval on chromosome 12q13

We have recently described a novel autosomal recessive disorder, lethal congenital contractural syndrome type 2 (LCCS2) (OMIM 607598), in a large Israeli Bedouin kindred. The phenotype, which is lethal in the neonatal period, is distinguished by the presence of a markedly distended urinary bladder. Association of LCCS2 to the known loci associated with arthogryposis was excluded. In the present study, we set out to determine the genetic locus harboring the gene defective in this disease. We performed genome-wide linkage analysis, demonstrating linkage to a approximately 6 cM (corresponding to approximately 7.2 Mb) homozygosity region on chromosome 12q13 between markers D12S1604 and D12S83. Based on recombination events, the interval harboring the disease-associated locus was further narrowed to a region spanning approximately 6 cM ( approximately 6.4 Mb) between D12S325 and D12S1072. Linkage of LCCS2 to that locus was established, with two significant maximum peaks at markers D12S1604 (Z(max) = 10.56 at theta = 0.01) and D12S1700 (Z(max) = 9.23 at theta = 0.00).

Sex ratio and proportion of affected sons in sibships with X-chromosomal recessive traits: maximum likelihood estimation in truncated multinomial distributions

If mothers are carriers of a recessive male sex-linked disorder, their children may include females, healthy males and affected males. The composition of the possible sibships follows a multinomial distribution. If the mothers are diagnosed as carriers independently of their offspring, then the distributions are not truncated, but if they are classified as carriers after the birth of at least one affected son, the distributions are truncated. In order to avoid ascertainment bias, the statistical analyses of the corresponding data must differ. We present procedures for estimation in both the untruncated and the truncated case. The formulae obtained are applied to family data for X-chromosomal recessive retinoschisis (RS) from the region of Satakunta in southwestern Finland. Earlier studies indicated that, among the offspring of RS carriers, the sex ratio was increased. In our model, therefore, we include both the proportion of males and the proportion of affected individuals among the males. The sex ratio was significantly increased (131.0), but the proportion of affected males was slightly lower than expected (42.5%). RS seems to be the only known genetic disorder in which the offspring of carriers of the mutation include a statistically significant surplus of males.

Molecular basis of autosomal recessive diseases among the Palestinian Arabs

In the review of the literature, 71 different autosomal recessive diseases have been delineated that are relatively frequent among Palestinian Arabs. Among those, in 40 the mutation(s) responsible for the diseases are known. Fourteen of these disorders were caused by a single mutation, while the other 26 were due to multiple mutations. Most of the mutations were found in homozygosity among the affected patients. It is probable that the high frequency of most of the genetic diseases among the Palestinian Arabs is due to a founder effect as the result of the high consanguinity rates in this population. However, in some cases the high frequency was demonstrated to be secondary to the presence of multiple mutations, either allelic or in different genes in a small geographic region. This phenomenon remains unexplained but may be secondary to a selective advantage to the carriers, either specific to the region or to the population.

Fine mapping places the gene for arthrogryposis multiplex congenita neuropathic type between D5S394 and D5S2069 on chromosome 5qter

Arthrogryposis multiplex congenita (AMC) is a heterogeneous symptom complex characterized by non-progressive joint contractures from birth that involve more than one part of the body. In 1997, our group investigated a large Israeli Arab inbred kindred that showed autosomal recessive inheritance of AMC neuropathic type, and we mapped the gene to 5qter between markers D5S1456 and D5S498. Haplotype sharing studies revealed complete homozygosity in all affected individuals with marker D5S394, thus providing significant statistical evidence in favor of linkage. In this study, we have undertaken further fine mapping of this region of chromosome 5qter, and have examined several additional markers. All the affected individuals showed complete homozygosity for the marker D5S394, and also for three additional markers that are telomeric to marker D5S394 and situated 31766 bp, 58016 bp, and 58516 bp, respectively, from it. Analysis of the recombinant individuals has enabled us to narrow down the critical region to a distance of.442 Mb between markers D5S394 and D5S2069.

Dual trafficking of Slit3 to mitochondria and cell surface demonstrates novel localization for Slit protein

Drosophila slit is a secreted protein involved in midline patterning. Three vertebrate orthologs of the fly slit gene, Slit1, 2, and 3, have been isolated. Each displays overlapping, but distinct, patterns of expression in the developing vertebrate central nervous system, implying conservation of function. However, vertebrate Slit genes are also expressed in nonneuronal tissues where their cellular locations and functions are unknown. In this study, we characterized the cellular distribution and processing of mammalian Slit3 gene product, the least evolutionarily conserved of the vertebrate Slit genes, in kidney epithelial cells, using both cellular fractionation and immunolabeling. Slit3, but not Slit2, was predominantly localized within the mitochondria. This localization was confirmed using immunoelectron microscopy in cell lines and in mouse kidney proximal tubule cells. In confluent epithelial monolayers, Slit3 was also transported to the cell surface. However, we found no evidence of Slit3 proteolytic processing similar to that seen for Slit2. We demonstrated that Slit3 contains an NH(2)-terminal mitochondrial localization signal that can direct a reporter green fluorescent protein to the mitochondria. The equivalent region from Slit1 cannot elicit mitochondrial targeting. We conclude that Slit3 protein is targeted to and localized at two distinct sites within epithelial cells: the mitochondria, and then, in more confluent cells, the cell surface. Targeting to both locations is driven by specific NH(2)-terminal sequences. This is the first examination of Slit protein localization in nonneuronal cells, and this study implies that Slit3 has potentially unique functions not shared by other Slit proteins.

Functional implications of the spectrum of mutations found in 234 cases with X-linked juvenile retinoschisis. The Retinoschisis Consortium

X-linked retinoschisis (XLRS) is the most common cause of juvenile macular degeneration in males, resulting in vision loss early in life. The gene involved in XLRS was identified recently. It encodes a protein with a disoidin domain, suggested to be involved in cell-cell interactions. We have screened the gene for mutations in 234 familial and sporadic retinoschisis cases and identified 82 different mutations in 214 (91%). Thirty one mutations were found more than once, i.e. 2-10 times, with the exception of the 214G-->A mutation which was found in 34 apparently unrelated cases. The origin of the patients, the linkage data and the site of the mutations (mainly CG dinucleotides) indicate that most recurrent mutations had independent origins and thus suggest the existence of a significant new mutation rate in XLRS1. The mutations identified cover the entire spectrum, from small intra-genic deletions (7%), to nonsense (6%), missense (75%), small frameshifting insertions/deletions (6%) and splice site mutations (6%). Since, regardless of the mutation type, no females with a typical RS phenotype were identified, RS seems to be caused by loss-of-function mutations only. Mutations occurred non-randomly, with hotspots at several CG dinucleotides and a C6stretch. Exons 1-3 contained few, mainly translation-truncating mutations, arguing against an important functional role for this segment of the protein. Exons 4-6, encoding the discoidin domain, contained most, mainly missense mutations. An alignment of 32 discoidin domain proteins was constructed to reveal the consensus sequence and to deduce the functional importance of the missense mutations identified. The mutation analysis revealed a high preponderance of mutations involving or creating cysteine residues, pointing to sites important for the tertiary folding and/or protein function, and highlights several amino acids which may be involved in XLRS1-specific protein-protein interactions. Despite the enormous mutation heterogeneity, patients have relatively uniform clinical manifestations although with great intra-familial variation in age at onset and progression.