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The filamins are a family of cytoplasmic proteins that bind to and organize actin filaments, link membrane proteins to the cytoskeleton, and provide a scaffold for signaling molecules. Mutations in the gene encoding filamin B (FLNB) cause a spectrum of osteochondrodysplasias, including atelosteogenesis type I (AOI) and atelosteogenesis type III (AOIII). AOI and AOIII are autosomal dominant lethal skeletal dysplasias characterized by overlapping clinical findings that include vertebral abnormalities, disharmonious skeletal maturation, hypoplastic long bones, and joint dislocations. Previous studies have shown that heterozygosity for missense mutations that alter the CH2 domain and repeat 6 region of filamin B produce AOI and AOIII. In this study, 14 novel missense mutations in FLNB were found in 15 unrelated patients with AOI and AOIII. The majority of the mutations resided in exon 2 and exon 3, which encode the CH2 domain of the actin,binding region of filamin B. The remaining mutations were found in exon 28 and exon 29, which encode repeats 14 and 15 of filamin B. These results show that clustering of mutations in two regions of FLNB produce AOI/AOIII, and highlight the important role of this cytoskeletal protein in normal skeletogenesis. Hum Mutat 27(7), 705-710,2006. Published 2006 Wiley,Liss, Inc.(dagger).

We aimed to assess the frequency of connective tissue abnormalities among patients with cerebrospinal fluid (CSF) leaks in a prospective study using a large cohort of patients. We enrolled a consecutive group of 50 patients, referred for consultation because of CSF leak. All patients have been carefully examined for the presence of connective tissue abnormalities, and based on findings, patients underwent genetic testing. Ancillary diagnostic studies included echocardiography, eye exam, and histopathological examinations of skin and dura biopsies in selected patients. We identified nine patients with heritable connective tissue disorders, including Marfan syndrome, Ehlers–Danlos syndrome and other unclassified forms. In seven patients, spontaneous CSF leak was the first noted manifestation of the genetic disorder. We conclude that spontaneous CSF leaks are associated with a spectrum of connective tissue abnormalities and may be the first noted clinical presentation of the genetic disorder. We propose that there is a clinical basis for considering spontaneous CSF leak as a clinical manifestation of heritable connective tissue disorders, and we suggest that patients with CSF leaks should be screened for connective tissue and vascular abnormalities.

The spondylometaphyseal dysplasias (SMDs) are a group of short-stature disorders distinguished by abnormalities in the ver-tebrae and the metaphyses of the tubular bones. SMD Kozlowski type (SMDK) is a well-defined autosomal-dominant SMD characterized by significant scoliosis and mild metaphyseal abnormalities in the pelvis. The vertebrae exhibit platyspondyly and overfaced pedicles similar to autosomal-dominant brachyolmia, which can result from heterozygosity for activating mutations in the gene encoding TRPV4, a calcium-permeable Ion channel. Mutation analysis in six out of six patients with SMDK demonstrated heterozygosity for missense mutations in TRPV4, and one mutation, predicting a R594H substitution, was recurrent in four patients. Similar to autosomal-dominant brachyolmia, the mutations altered basal calcium channel activity in vitro. Metatropic dysplasia is another SMD that has been proposed to have both clinical and genetic heterogeneity. Patients with the nonlethal form of metatropic dysplasia present with a progressive scoliosis, widespread metaphyseal involvement of the appendicular skeleton, and carpal ossification delay. Because of some similar radiographic features between SMDK and metatropic dysplasia, 'FRPV4 was tested as a disease gene for nonlethal metatropic dysplasia. In two sporadic cases, heterozygosity for de novo missense mutations in TRPV4 was found. The findings demonstrate that mutations in TRPV4 produce a phenotypic spectrum of skeletal dysplasias from the mild autosomal-dominant brachyolmia to SMDK to autosomal-dominant metatropic dysplasia, suggesting that these disorders should be grouped into a new bone dysplasia family. ispartof: American Journal of Human Genetics vol:84 issue:3 pages:307-315 ispartof: location:United States status: published

Background: Larsen syndrome is an autosomal dominant osteochondrodysplasia characterised by large-joint dislocations and craniofacial anomalies. Recently, Larsen syndrome was shown to be caused by missense mutations or small inframe deletions in FLNB, encoding the cytoskeletal protein filamin B. To further delineate the molecular causes of Larsen syndrome, 20 probands with Larsen syndrome together with their affected relatives were evaluated for mutations in FLNB and their phenotypes studied.Methods: Probands were screened for mutations in FLNB using a combination of denaturing high-performance liquid chromatography, direct sequencing and restriction endonuclease digestion. Clinical and radiographical features of the patients were evaluated.Results and discussion: The clinical signs most frequently associated with a FLNB mutation are the presence of supernumerary carpal and tarsal bones and short, broad, spatulate distal phalanges, particularly of the thumb. All individuals with Larsen syndrome-associated FLNB mutations are heterozygous for either missense or small inframe deletions. Three mutations are recurrent, with one mutation, 5071G -> A, observed in 6 of 20 subjects. The distribution of mutations within the FLNB gene is non-random, with clusters of mutations leading to substitutions in the actin-binding domain and filamin repeats 13-17 being the most common cause of Larsen syndrome. These findings collectively define autosomal dominant Larsen syndrome and demonstrate clustering of causative mutations in FLNB.

Background: The majority of COL2A1 missense mutations are substitutions of obligatory glycine residues in the triple helical domain. Only a few non-glycine missense mutations have been reported and among these, the arginine to cysteine substitutions predominate. Objective: To investigate in more detail the phenotype resulting from arginine to cysteine mutations in the COL2A1 gene. Methods: The clinical and radiographic phenotype of all patients in whom an arginine to cysteine mutation in the COL2A1 gene was identified in our laboratory, was studied and correlated with the abnormal genotype. The COL2A1 genotyping involved DHPLC analysis with subsequent sequencing of the abnormal fragments. Results: Six different mutations (R75C, R365C, R519C, R704C, R789C, R1076C) were found in 11 unrelated probands. Each mutation resulted in a rather constant and site-specific phenotype, but a perinatally lethal disorder was never observed. Spondyloarthropathy with normal stature and no ocular involvement were features of patients with the R75C, R519C, or R1076C mutation. Short third and/or fourth toes was a distinguishing feature of the R75C mutation and brachydactyly with enlarged finger joints a key feature of the R1076C substitution. Stickler dysplasia with brachydactyly was observed in patients with the R704C mutation. The R365C and R789C mutations resulted in classic Stickler dysplasia and spondyloepiphyseal dysplasia congenita (SEDC), respectively. Conclusions: Arginine to cysteine mutations are rather infrequent COL2A1 mutations which cause a spectrum of phenotypes including classic SEDC and Stickler dysplasia, but also some unusual entities that have not yet been recognised and described as type II collagenopathies.

Opsismodysplasia ( opsismos in Greek = late) is a rare chondrodysplasia, first described in 1977 by Zonana et al 1 as a unique chondrodysplasia and designated “opsismodysplasia” only in 1984.2 The disorder is characterised clinically by micromelia with extremely short hands and feet and respiratory distress responsible for death in the first few years of life.2 The main radiological features include severe platyspondyly, major delay in skeletal ossification, and metaphyseal cupping. To date, 13 cases have been reported and recurrence in sibs and/or consanguinity have suggested an autosomal recessive mode of inheritance.1–6 Here, we describe the clinical, radiological and chondro-osseous findings of 12 previously unreported cases in nine families. We show that opsismodysplasia is not a consistently lethal condition and we identify the severity of the delayed bone ossification as an important feature, distinct from other forms of spondylo(epi)metaphyseal dysplasias. Seven male and five female cases originating from nine families of French (4/9), German, (1/9), and Algerian origin (4/9) were included in the study. All affected cases presented with the following inclusion criteria: (1) major delay in epiphyseal ossification, (2) platyspondyly, (3) metaphyseal cupping, and (4) very short metacarpals and phalanges. Half of the cases were prenatally diagnosed during ultrasound follow up of the pregnancies and half of them were diagnosed postnatally. Pregnancies were terminated between 15 and 29 weeks’ of gestation. For chondro-osseous studies, the samples were embedded in paraffin and HES routinely stained after fixation in 4% formaldehyde and decalcification with EDTA. ### Key points

To further delineate and classify those forms of short trunk dwarfism characterized by multiple vertebral segmentation defects, we analyzed 26 new patients and reviewed 115 described in the literature. Three distinct entities were recognized based on radio-graphic and clinical findings. Jarcho-Levin syndrome is the lethal autosomal recessive form, characterized by a symmetric crablike chest. Spondylocostal dysostosis is the benign autosomal dominant condition. Spondylothoracic dysostosis shows considerable clinical and radiographic overlap with spondylocostal dysostosis. Malformations observed in association with multiple vertebral segmentation defects are more common in the sporadic patients. Analysis of the 26 new individuals revealed that the body segment in which these nonvertebral malformations occur corresponds to the site of the vertebral segmentation defects. © 1996 Wiley-Liss, Inc.

Multiple epiphyseal dysplasia (MED) is a dominantly inherited chondrodysplasia characterized by mild short stature and early-onset osteoarthrosis. Some forms of MED clinically resemble another chondrodysplasia phenotype, the mild form of pseudoachondroplasia (PSACH). On the basis of their clinical similarities as well as similar ultrastructural and biochemical features in cartilage from some patients, it has been proposed that MED and PSACH belong to a single bone-dysplasia family. Recently, both mild and severe PSACH as well as a form of MED have been linked to the same interval on chromosome 19, suggesting that they may be allelic disorders. Linkage studies with the chromosome 19 markers were carried out in a large family with MED and excluded the previously identified interval. Using this family, we have identified an MED locus on the short arm of chromosome 1, in a region containing the gene (COL9A2) that encodes the alpha 2 chain of type IX collagen, a structural component of the cartilage extracellular matrix.

We have characterized a mutation in the type II collagen gene (COL2A1) that produces a form of spondyloepiphyseal dysplasia. The mutation is an internal tandem duplication of 45 base pairs within exon 48 and results in the addition of 15 amino acids to the triple-helical domain of the alpha 1 chains of type II collagen derived from the abnormal allele. Although the repeating (Gly-Xaa-Yaa)n motif that characterizes the triple-helical domain is preserved, type II collagen derived from cartilage of the affected individual contains a population with excessive posttranslational modification, consistent with a disruption in triple-helix structure. The mutation is not carried by either parent, indicating that the phenotype in the affected individual is due to a new dominant mutation. DNA sequence homology in the area of the duplication suggests that the mutation may have arisen by unequal crossover between related sequences, a proposed mechanism in the evolution and diversification of the collagen gene family.

The short-rib polydactyly (SRP) syndromes are a heterogeneous group of perinatal lethal skeletal disorders with polydactyly and multisystem organ abnormalities. Homozygosity by descent mapping in a consanguineous SRP family identified a genomic region that contained DYNC2H1, a cytoplasmic dynein involved in retrograde transport in the cilium. Affected individuals in the family were homozygous for an exon 12 missense mutation that predicted the amino acid substitution R587C. Compound heterozygosity for one missense and one null mutation was identified in two additional nonconsanguineous SRP families. Cultured chondrocytes from affected individuals showed morphologically abnormal, shortened cilia. In addition, the chondrocytes showed abnormal cytoskeletal microtubule architecture, implicating an altered microtubule network as part of the disease process. These findings establish SRP as a cilia disorder and demonstrate that DYNC2H1 is essential for skeletogenesis and growth.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are autosomal dominant osteochondrodysplasias that result in mild to severe short-limb dwarfism and early-onset osteoarthrosis. PSACH and some forms of MED result from mutations in the gene for cartilage oligomeric matrix protein (COMP; OMIM 600310 [http://www3.ncbi.nlm. nih.gov:80/htbin-post/Omim/dispmim?600310]). We report the identification of COMP mutations in an additional 14 families with PSACH or MED phenotypes. Mutations predicted to result in single-amino acid deletions or substitutions, all in the region of the COMP gene encoding the calmodulin-like repeat elements, were identified in patients with moderate to severe PSACH. We also identified within this domain a missense mutation that produced MED Fairbank. In two families, one with mild PSACH and the second with a form of MED, we identified different substitutions for a residue in the carboxyl-terminal globular region of COMP. Both the clinical presentations of these two families and the identification of COMP-gene mutations provide evidence of phenotypic overlap between PSACH and MED. These data also reveal a role for the carboxyl-terminal domain in the structure and/or function of COMP.

Background Magnetic resonance imaging (MRI) is used as an adjunct to ultrasound in prenatal imaging, the latter being the standard technique in obstetrical medicine. Methods Initial results demonstrate the ability to visualise the foetal skeleton and muscles on MRI, and highlight the potentially useful applications for foetal MRI, which has significantly profited from innovations in sequence technology. Echoplanar imaging, thick-slab T2-weighted (w) imaging, and dynamic sequences are techniques complementary to classical T2-w imaging. Results Recent study data indicate that foetal MRI may be useful in the imaging of spinal dysraphism and in differentiating between isolated and complex skeletal deformities with associated congenital malformations, which might have an impact on pre- and postnatal management. Conclusion More research and technical refinement will be necessary to investigate normal human skeletal development and to identify MR imaging characteristics of skeletal abnormalities.

View Large Image | View Hi-Res Image | Download PowerPoint SlideThe human genetics community has lost one of its giants. Maimon Cohen was an early leader in the field of human genetics and played a pivotal role in its growth and development. His impact, both nationally and internationally, was extraordinary, both in science and in education.He grew up in Baltimore, MD, where he earned his bachelor’s degree in Semitic languages from Johns Hopkins in 1955. Dr. Cohen planned to be an agronomist and earned a master’s degree in 1959 and a doctorate in crop genetics from the University of Maryland in 1962. He planned to move to Israel to practice crop genetics, but, while doing a postdoctoral fellowship at the University of Michigan, he became interested in human genetics. There, under the tutelage of Margery Shaw, he became an accomplished cytogeneticist.In 1965, he moved to the Department of Pediatrics at the State University of New York at Buffalo as the Director of Cytogenetics in the Division of Human Genetics, and he quickly rose to the rank of Associate Professor of Pediatrics and Microbiology in 1968. In addition to making a number of fundamental discoveries in human cytogenetics in Buffalo, he also wrote a fascinating paper on the chromosomes of five crocodilian species. He showed a broad interest in other aspects of biology, including a series of experiments in mice published by him and Anil Mukherjee in Nature in 1970 that was perhaps the first demonstration that in vitro fertilization does not have deleterious effects on the embryo.In 1972, he was appointed Professor and Chairman of the Department of Human Genetics at Hadassah Hebrew University Medical School in Jerusalem, where he developed a vibrant department and where his legacy remains evident to this day. In that year, he was also the lead author in the publication of the first of the vital books on standardization of human cytogenetics. In Israel, he continued to be a leader in the study of chromosomes and somatic cell genetics and became involved in the clinical and biochemical descriptions of a number of genetic disorders. A major paper written with his successor in the chair, Gideon Bach, demonstrated the basic biochemical defect in mucolipidosis IV.In 1979, he returned to the United States as Associate Head of the Division of Genetics for the Children’s Memorial Hospital in Chicago and was appointed Professor of Pediatrics at Northwestern University Medical School. While continuing his collaboration and publishing papers with his Israeli colleagues, he began a series of experiments with his Chicago associates on chemical and radiation sensitivity in cells from patients with ataxia telangiectasia and other chromosomal breakage syndromes.In 1982, he became the Chief of the Division of Human Genetics at the University of Maryland School of Medicine and Professor of both Obstetrics and Gynecology and Pediatrics. Other positions he held during his stay at the University of Maryland were a professorship in the Medical Biotechnology Center, Vice Chair of Obstetrics and Gynecology, and Professor of Pathology. While at Maryland, he trained and collaborated with a number of cytogeneticists and human geneticists, including such leaders in the field as Stuart Schwartz, Joel Charrow, Susan Panny, Miriam Blitzer, and the present Executive Vice President of the American Society for Human Genetics, Joann Boughman. During this period, he continued his important work in human and animal cytogenetics and furthered our understanding of chromosome damage caused by a variety of environmental factors.In 1998, he became the first director of the Harvey Institute for Human Genetics at the Greater Baltimore Medical Center, where he developed a busy and highly respected cytogenetic service laboratory while continuing to publish original papers in human cytogenetics.Dr. Cohen made enormous contributions to the evolution of genetics into a full medical and scientific specialty. He was elected to a number of important offices, including Director, Treasurer, and President of the American Society of Human Genetics, the latter in 1994. He was one of the organizers of the American College of Medical Genetics and was one of its Directors for seven years, during which time he was the Vice President for Laboratory Genetics. Dr. Cohen had a major interest in governmental affairs. In 1995, he spent a year as a Legislative Assistant, Health Affairs, to U.S. Senator Paul D. Wellstone, as an American Association for the Advancement of Science and Engineering Congressional Fellow sponsored by the American Society of Human Genetics. He held numerous grants both in the United States and in Israel and published 221 peer-reviewed papers in the most prestigious journals in our field.Maimon Cohen was one of the great leaders in the field of human genetics and most particularly in human cytogenetics. A man of indomitable spirit, Dr. Cohen is remembered by his colleagues and friends for his enormous energy, his inspirational leadership, and his compassionate mentoring skills. He is survived by Barbara, his wife of 51 years, and by their three sons Neri, Akiva, and Noam and their families. Each of their sons is continuing Maimon’s commitment to science. His legacy is permanent. We will all miss him and his intelligence and humor.