Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
 ...
PMID:Mutation of TBCE causes hypoparathyroidism-retardation-dysmorphism and autosomal recessive Kenny-Caffey syndrome. 1238 28

Microtubules are indispensable dynamic structures that contribute to many essential biological functions. Assembly of the native alpha/beta tubulin heterodimer, the subunit that polymerizes to form microtubules, requires the participation of several molecular chaperones, namely prefoldin, the cytosolic chaperonin CCT, and a series of five tubulin-specific chaperones termed cofactors A-E (TBCA-E). Among these, TBCC, TBCD, and TBCE are essential in higher eukaryotes; they function together as a multimolecular machine that assembles quasinative CCT-generated alpha- and beta-tubulin polypeptides into new heterodimers. Deletion and truncation mutations in the gene encoding TBCE have been shown to cause the rare autosomal recessive syndrome known as HRD, a devastating disorder characterized by congenital hypoparathyroidism, mental retardation, facial dysmorphism, and extreme growth failure. Here we identify cryptic translational initiation at each of three out-of-frame AUG codons upstream of the genetic lesion as a unique mechanism that rescues a mutant HRD allele by producing a functional TBCE protein. Our data explain how afflicted individuals, who would otherwise lack the capacity to make functional TBCE, can survive and point to a limiting capacity to fold tubulin heterodimers de novo as a contributing factor to disease pathogenesis.
 ...
PMID:Cryptic out-of-frame translational initiation of TBCE rescues tubulin formation in compound heterozygous HRD. 1693 82

Hypoparathyroidism-retardation-dysmorphism (HRD; Sanjad-Sakati Syndrome; Online Mendelian Inheritance in Man [OMIM] #241410) is a rare recessive syndrome predominantly seen on the Arabian Peninsula and characterized by congenital hypoparathyroidism, intrauterine growth retardation, mental retardation, seizures, and a typical facial dysmorphism (prominent forehead, deep-set eyes, and abnormal external ears).(1,2) To date, the same homozygous deletion in TBCE (155-166del) has been reported in all Saudi Arabian patients with HRD(1) as well as in all Saudi Arabian patients with Kenny-Caffey syndrome (OMIM #244460),(1) a syndrome with a phenotype that resembles that of HRD but is characterized by the presence of normal intelligence, late closure of the anterior fontanelle, macrocephaly, and postnatal (rather than prenatal) growth retardation.(1,3) Nanophthalmos and corneal opacity have been documented in Kenny-Caffey syndrome patients,(4) but ocular disease has not been well-described in HRD. We describe the ocular features of four Saudi Arabian HRD children referred to our institution for ocular complaints noted by their parents.
 ...
PMID:Ophthalmic features of hypoparathyroidism-retardation-dysmorphism. 1725 73

Kenny-Caffey syndrome (KCS) is a rare dysmorphologic syndrome characterized by proportionate short stature, cortical thickening and medullary stenosis of tubular bones, delayed closure of anterior fontanelle, eye abnormalities, and hypoparathyroidism. The autosomal dominant form of KCS (KCS type 2 [KCS2]) is distinguished from the autosomal recessive form of KCS (KCS type 1 [KCS1]), which is caused by mutations of the tubulin-folding cofactor E (TBCE) gene, by the absence of mental retardation. In this study, we recruited four unrelated Japanese patients with typical sporadic KCS2, and performed exome sequencing in three patients and their parents to elucidate the molecular basis of KCS2. The possible candidate genes were explored by a de novo mutation detection method. A single gene, FAM111A (NM_001142519.1), was shared among three families. An identical missense mutation, R569H, was heterozygously detected in all three patients but not in the unaffected family members. This mutation was also found in an additional unrelated patient. These findings are in accordance with those of a recent independent report by a Swiss group that KCS2 is caused by a de novo mutation of FAM111A, and R569H is a hot spot mutation for KCS2. Although the function of FAM111A is not known, this study would provide evidence that FAM111A is a key molecule for normal bone development, height gain, and parathyroid hormone development and/or regulation.
 ...
PMID:A recurrent de novo FAM111A mutation causes Kenny-Caffey syndrome type 2. 2399 31

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.
...
PMID:Sanjad-Sakati syndrome in a Tunisian child. 2623 22