The autosomal recessive Kenny-Caffey syndrome locus maps to chromosome 1q42-q43

Fine mapping of bone structure and strength QTLs in heterogeneous stock rat

We previously demonstrated that skeletal structure and strength phenotypes vary considerably in heterogeneous stock (HS) rats. These phenotypes were found to be strongly heritable, suggesting that the HS rat model represents a unique genetic resource for dissecting the complex genetic etiology underlying bone fragility. The purpose of this study was to identify and localize genes associated with bone structure and strength phenotypes using 1524 adult male and female HS rats between 17 to 20 weeks of age. Structure measures included femur length, neck width, head width; femur and lumbar spine (L3-5) areas obtained by DXA; and cross-sectional areas (CSA) at the midshaft, distal femur and femoral neck, and the 5th lumbar vertebra measured by CT. In addition, measures of strength of the whole femur and femoral neck were obtained. Approximately 70,000 polymorphic SNPs distributed throughout the rat genome were selected for genotyping, with a mean linkage disequilibrium coefficient between neighboring SNPs of 0.95. Haplotypes were estimated across the entire genome for each rat using a multipoint haplotype reconstruction method, which calculates the probability of descent at each locus from each of the 8 HS founder strains. The haplotypes were then tested for association with each structure and strength phenotype via a mixed model with covariate adjustment. We identified quantitative trait loci (QTLs) for structure phenotypes on chromosomes 3, 8, 10, 12, 17 and 20, and QTLs for strength phenotypes on chromosomes 5, 10 and 11 that met a conservative genome-wide empiric significance threshold (FDR=5%; P<3×10(-6)). Importantly, most QTLs were localized to very narrow genomic regions (as small as 0.3 Mb and up to 3 Mb), each harboring a small set of candidate genes, both novel and previously shown to have roles in skeletal development and homeostasis.

Sanjad-Sakati syndrome in a Tunisian child

Sanjad-Sakati syndrome (SSS) (OMIM 241410) is a rare autosomal recessive disorder characterized by congenital hypoparathyroidism with growth and mental retardation associated with seizures and a characteristic physiognomy. SSS molecular pathology has been shown to be due to mutations in the TBCE gene on chromosome 1q42-q43. All affected patients of Arab origin are homozygous for a 12-bp (155-166del) deletion in exon 3 of this gene. We report on a Tunisian child with SSS who was homozygous for the 155-166del mutation. Our findings provide additional support of the common (155-166del) deletion founder effect in exon 3 of the TBCE gene in Arab patients. It is very likely that this mutation originated in the Middle East and was introduced in Tunisia by the Banu Hilal invaders.

New Ocular Associations in Sanjad-Sakati Syndrome: Case report from Oman

Sanjad-Sakati syndrome (SSS; Online Mendelian Inheritance in Man [OMIM] #241410), also known as hypoparathyroidism-retardation-dysmorphism (HRD) syndrome, is an autosomal recessive disorder in which prenatal-onset extreme growth retardation, congenital hypoparathyroidism and craniofacial dysmorphism result from mutations in the tubulin-specific chaperone E (TBCE) gene on chromosome 1q42-43. We report unique ophthalmic findings in a two-year-old child with molecularly confirmed SSS, who was admitted to Sultan Qaboos University Hospital in Oman at 11 weeks old with bilateral congenital corneal clouding. The ophthalmic findings in this patient were linked to faulty microtubule assembly in the brain, abnormal intracellular membrane transport and the resulting metabolic derangement seen in patients with SSS.

Neurological manifestations in children with Sanjad-Sakati syndrome

Background:

Sanjad–Sakati syndrome (SSS), also known as hypoparathyroidism–mental retardation–dysmorphism syndrome, or HRD, is a rare disorder characterized by growth and developmental delay, and by mental retardation and dysmorphic features.

Objective:

The objective of this study was to clarify the clinical and neurological features of SSS.

Patients:

Twenty-four patients were included in the study. They were seen at two hospitals in Kuwait.

Methods:

This was a retrospective study of patients with SSS who attended the pediatric endocrinology, genetic, and neurology clinics in the Aladan and Alfarawanya hospitals in Kuwait from September 2007 to September 2012. Clinical and radiological data were obtained from each patient’s medical records.

Results:

All 24 patients had the characteristic dysmorphic features and laboratory findings of SSS. Consanguinity was reported in 75% of parents. Neurological manifestations in the form of microcephaly, developmental delay, mental retardation, and seizures were reported in all patients. Computerized tomography scans and/or magnetic resonance imaging showed evidence of intracranial calcifications in 29.2% of patients. Two patients showed a thin corpus callosum, and one patient showed intraventricular hemorrhaging.

Conclusion:

Patients with SSS display a variety of dysmorphic features and neurological manifestations, including microcephaly, mental retardation, intracranial calcification, and epilepsy.

Parathyroid and autoimmunity

Data in favor of chronic hypoparathyroidism as an autoimmune disease are examined. The article takes into consideration the different clinical forms, genetic patterns, histopathology, animal models, cellular immunity, circulating autoantibodies, target autoantigens, clinical manifestations, laboratory diagnosis and therapy. Furthermore, data on 71 Italian patients with chronic hypoparathyroidism are presented.

Novel human, mouse and xenopus genes encoding a member of the RAS superfamily of low-molecular-weight GTP-binding proteins and its downregulation in W/WV mouse jejunum

BACKGROUND AND AIM

Interstitial cells of Cajal (ICC) are pacemakers and mediators of neurotransmission in gastroenteric smooth muscles. Interstitial cells of Cajal require cellular signaling via KIT, a receptor tyrosine kinase, for development and maintenance of cellular phenotype. Much of the evidence demonstrating the functions of ICC comes from studies of W/W V mutant mice, which have reduced KIT function. The aim of the present study was to differentially examine gene expression in the small intestines of wild-type and W/W V mice.

METHODS

RNA from the jejunum of wild-type and W/W V mice was analyzed using a differential gene display method.

RESULTS

One candidate gene, encoding a novel small GTPase of the RAS superfamily, was significantly suppressed both in fed and starved W/WV mice. The full-length clone of the murine gene and its human and xenopus counterparts were designated GTP-binding protein, 28 kDa (G28K). Human G28K cDNA encodes a protein of 258 amino acids with homology to the human cell division cycle 42/G25K protein. This gene is located at 1q42.11-q42.3. G28K was abundantly expressed in the human stomach and the small intestine. Semi-quantitative reverse transcription-polymerase chain reaction analysis revealed expression of G28K mRNA within single isolated ICC.

CONCLUSIONS

Gene analysis showed that G28K was differentially expressed in the small intestines of wild-type and W/W V mice. Interstitial cells of Cajal within the small intestine expressed mRNA for G28K. The specific downregulation of G28K in the jejunum of W/W V mice, and high expression in human intestinal tissue suggest that the G28K gene might be associated with ICC function in mice and in humans.

Mutations in the chemokine receptor gene CXCR4 are associated with WHIM syndrome, a combined immunodeficiency disease

WHIM syndrome is an immunodeficiency disease characterized by neutropenia, hypogammaglobulinemia and extensive human papillomavirus (HPV) infection. Despite the peripheral neutropenia, bone marrow aspirates from affected individuals contain abundant mature myeloid cells, a condition termed myelokathexis. The susceptibility to HPV is disproportionate compared with other immunodeficiency conditions, suggesting that the product of the affected gene may be important in the natural control of this infection. We describe here the localization of the gene associated with WHIM syndrome to a region of roughly 12 cM on chromosome 2q21 and the identification of truncating mutations in the cytoplasmic tail domain of the gene encoding chemokine receptor 4 (CXCR4). Haplotype and mutation analyses in a pedigree transmitting myelokathexis as an apparently autosomal recessive trait support genetic heterogeneity for this aspect of the WHIM syndrome phenotype. Lymphoblastoid cell lines carrying a 19-residue truncation mutation show significantly greater calcium flux relative to control cell lines in response to the CXCR4 ligand, SDF-1, consistent with dysregulated signaling by the mutant receptor. The identification of mutations in CXCR4 in individuals with WHIM syndrome represents the first example of aberrant chemokine receptor function causing human disease and suggests that the receptor may be important in cell-mediated immunity to HPV infection.

International nosology and classification of constitutional disorders of bone (2001)

The last International Classification of Constitutional Disorders of Bone was published in 1998. Since then rapid advances have been made in identifying the molecular changes responsible for defined conditions and new disorders are constantly being delineated. For these reasons a further update on the classification is appropriate. It has been expended to not only the osteochondrodysplasias (33 groups) but also genetically determined dysostoses (3 groups).

Mutation of TBCE causes hypoparathyroidism-retardation-dysmorphism and autosomal recessive Kenny-Caffey syndrome

The syndrome of congenital hypoparathyroidism, mental retardation, facial dysmorphism and extreme growth failure (HRD or Sanjad-Sakati syndrome; OMIM 241410) is an autosomal recessive disorder reported almost exclusively in Middle Eastern populations. A similar syndrome with the additional features of osteosclerosis and recurrent bacterial infections has been classified as autosomal recessive Kenny-Caffey syndrome (AR-KCS; OMIM 244460). Both traits have previously been mapped to chromosome 1q43-44 (refs 5,6) and, despite the observed clinical variability, share an ancestral haplotype, suggesting a common founder mutation. We describe refinement of the critical region to an interval of roughly 230 kb and identification of deletion and truncation mutations of TBCE in affected individuals. The gene TBCE encodes one of several chaperone proteins required for the proper folding of alpha-tubulin subunits and the formation of alpha-beta-tubulin heterodimers. Analysis of diseased fibroblasts and lymphoblastoid cells showed lower microtubule density at the microtubule-organizing center (MTOC) and perturbed microtubule polarity in diseased cells. Immunofluorescence and ultrastructural studies showed disturbances in subcellular organelles that require microtubules for membrane trafficking, such as the Golgi and late endosomal compartments. These findings demonstrate that HRD and AR-KCS are chaperone diseases caused by a genetic defect in the tubulin assembly pathway, and establish a potential connection between tubulin physiology and the development of the parathyroid.

Autoimmune adrenal insufficiency and autoimmune polyendocrine syndromes: autoantibodies, autoantigens, and their applicability in diagnosis and disease prediction

Recent progress in the understanding of autoimmune adrenal disease, including a detailed analysis of a group of patients with Addison's disease (AD), has been reviewed. Criteria for defining an autoimmune disease and the main features of autoimmune AD (history, prevalence, etiology, histopathology, clinical and laboratory findings, cell-mediated andhumoral immunity, autoantigens and their autoepitopes, genetics, animal models, associated autoimmune diseases, pathogenesis, natural history, therapy) have been described. Furthermore, the autoimmune polyglandular syndromes (APS) associated with AD (revised classification, animal models, genetics, natural history) have been discussed. Of Italian patients with primary AD (n = 317), 83% had autoimmune AD. At the onset, all patients with autoimmune AD (100%) had detectable adrenal cortex and/or steroid 21-hydroxylase autoantibodies. In the course of natural history of autoimmune AD, the presence of adrenal cortex and/or steroid 21-hydroxylase autoantibodies identified patients at risk to develop AD. Different risks of progression to clinical AD were found in children and adults, and three stages of subclinical hypoadrenalism have been defined. Normal or atrophic adrenal glands have been demonstrated by imaging in patients with clinical or subclinical AD. Autoimmune AD presented in four forms: as APS type 1 (13% of the patients), APS type 2 (41%), APS type 4 (5%), and isolated AD (41%). There were differences in genetics, age at onset, prevalence of adrenal cortex/21-hydroxylase autoantibodies, and associated autoimmune diseases in these groups. "Incomplete" forms of APS have been identified demonstrating that APS are more prevalent than previously reported. A varied prevalence of hypergonadotropic hypogonadism in patients with AD and value of steroid-producing cells autoantibodies reactive with steroid 17alpha-hydroxylase or P450 side-chain cleavage enzyme as markers of this disease has been discussed. In addition, the prevalence, characteristic autoantigens, and autoantibodies of minor autoimmune diseases associated with AD have been described. Imaging of adrenal glands, genetic tests, and biochemical analysis have been shown to contribute to early and correct diagnosis of primary non-autoimmune AD in the cases of hypoadrenalism with undetectable adrenal autoantibodies. An original flow chart for the diagnosis of AD has been proposed.

Molecular and radiological diagnosis of sclerosing bone dysplasias

Bone mineral density (BMD) is a quantitative trait for which the heritability of the variance is estimated to be up to 80%, based on epidemiological and twin studies. Further illustration of the involvement of genetic factors in bone homeostasis, is the existence of an extended group of genetic conditions associated with an abnormal bone density. The group of conditions with increased bone density has long been poorly studied and understood at the molecular genetic level but recently, thanks to recent developments in molecular genetics and genomics, for some of them major breakthroughs have been made. These findings will make the molecular analysis of such patients an additional tool in diagnostics and in genetic counseling. However, the initial identification of affected patients is still largely dependent upon recognition of clinical and radiological stigmata of the disease. Therefore, in this overview of sclerosing bone dysplasias, the classical clinical and radiological signs of this group of disorders will be discussed along with the new molecular insights.

Prenatal diagnosis of hypoparathyroidism retardation and dysmorphism (HRD) syndrome

We used linkage analysis for prenatal diagnosis of the recently reported hypoparathyroidism, retardation, and dysmorphism (HRD) syndrome. Five cases from four families were evaluated. Three fetuses were carriers and were born healthy. Two fetuses were affected but the parents decided not to terminate the pregnancies. The diagnosis of HRD syndrome was confirmed in these newborns. This is the first report about prenatal diagnosis of HRD syndrome.

Sanjad-Sakati and autosomal recessive Kenny-Caffey syndromes are allelic: evidence for an ancestral founder mutation and locus refinement

The Sanjad-Sakati syndrome (SSS; MIM241410), an autosomal recessive trait characterized by congenital hypoparathyroidism, growth and mental retardation, seizures, and a characteristic physiognomy, was recently linked to chromosome area 1q42-q43. SSS resembles the autosomal recessive form of Kenny-Caffey syndrome (KCS; MIM244460), with similar manifestations but lacking osteosclerosis. Since KCS was recently linked to the region 1q42-q43, the possibility that this disorder is allelic with SSS was considered. Eight Sanjad-Sakati families from Saudi Arabia were genotyped with polymorphic short tandem repeat markers from the SSS/KCS critical region. A maximum multipoint LOD score of 14.32 was obtained at marker D1S2649, confirming linkage of SSS to the same region as autosomal recessive KCS. Haplotype analysis refined the critical region to 2.6 cM and identified a rare haplotype present in all the SSS disease alleles, indicative of a common founder. In addition to the assignment of the Saudi SSS and Kuwaiti KCS syndromes to overlapping genetic intervals, comparison of the haplotypes unexpectedly demonstrated that the diseases shared an identical haplotype. This finding, combined with the clinical similarity between the two syndromes, suggests that the two conditions are not only allelic but are also caused by the same ancestral mutation.