STK25 is a candidate gene for pseudopseudohypoparathyroidism

Genotype-Phenotype Correlations in 2q37-Deletion Syndrome: An Update of the Clinical Spectrum and Literature Review

2q37 microdeletion/deletion syndrome (2q37DS) is one of the most common subtelomeric deletion disorders, caused by a 2q37 deletion of variable size. The syndrome is characterized by a broad and diverse spectrum of clinical findings: characteristic facial dysmorphism, developmental delay/intellectual disability (ID), brachydactyly type E, short stature, obesity, hypotonia in infancy, and abnormal behavior with autism spectrum disorder. Although numerous cases have been described so far, the exact mapping of the genotype and phenotype have not yet been achieved.

MATERIALS AND METHODS

In this study we analyzed nine newly diagnosed cases with 2q37 deletion (3 male/6 female, aged between 2 and 30 years old), and followed up at the Iasi Regional Medical Genetics Centre. All patients were tested first with MLPA using combined kits P036/P070 subtelomeric screening mix and follow-up mix P264; after, the deletion size and location were confirmed via CGH-array. We compared our findings with the data of other cases reported in the literature.

RESULTS

From nine cases, four had pure 2q37 deletions of variable sizes, and five presented deletion/duplication rearrangements (with chromosomes 2q, 9q, and 11p). In most cases, characteristic phenotypic aspects were observed: 9/9 facial dysmorphism, 8/9 global developmental delay and ID, 6/9 hypotonia, 5/9 behavior disorders, and 8/9 skeletal anomalies-especially brachydactyly type E. Two cases had obesity, one case had craniosynostosis, and four had heart defects. Other features found in our cases included translucent skin and telangiectasias (6/9), and a hump of fat on the upper thorax (5/9).

CONCLUSIONS

Our study enriches the literature data by describing new clinical features associated with 2q37 deletion, and possible genotype-phenotype correlations.

A patient with features of albright hereditory osteodystrophy and unusual neuropsychiatric findings without coding Gsalpha mutations

BACKGROUND

Pseudohypoparathyroidism(PHP) is a heterogeneous group of rare metabolic disorders characterized by hypocalcemia and hyperphosphatemia resulting from PTH resistance. Different forms of PHP have been reported based on biochemical and clinical manifestation and genetic findings. Most of these forms are caused by defects in GNAS, an imprinted gene locus with multiple subunits. We reported a 12- year- old girl with unusual clinical manifestations of Pseudopseudohypoparathyroidism(PPHP).

METHODS

After clinical and biochemical evaluations, the patients' genomic DNA was isolated from peripheral blood leukocytes using salting out method. The whole coding sequences of GNAS gene including 13 exons were amplified by PCR. Quantitative PCR reactions were performed too.

FINDINGS

We described a 12- year- old girl with Albright Hereditory osteodystrophy (AHO) phenotype, poor school performance, some abnormal movements, TSH resistance with normal serum calcium and phosphorus levels and normal Gsα bioactivity with no mutation in GNAS exons. Unusual neuropsychiatric findings in this patient were compatible with Asperger syndrome.

CONCLUSIONS

According to our findings this patient could not be categorized in any of PHP subgroups. Identifying of such individuals may be useful to discover different genetic patterns in pseudohypoparathyroidism and pseudopseudohypoparathyroidism. It is important to identify patients in whom PHP is caused by novel GNAS mutations, as careful investigations of these findings will likely further our knowledge of this complex and this unique disorder. In addition this case presented with unusual neuropsychiatric findings which has not been reported up to now.

SOcK, MiSTs, MASK and STicKs: the GCKIII (germinal centre kinase III) kinases and their heterologous protein-protein interactions

The GCKIII (germinal centre kinase III) subfamily of the mammalian Ste20 (sterile 20)-like group of serine/threonine protein kinases comprises SOK1 (Ste20-like/oxidant-stress-response kinase 1), MST3 (mammalian Ste20-like kinase 3) and MST4. Initially, GCKIIIs were considered in the contexts of the regulation of mitogen-activated protein kinase cascades and apoptosis. More recently, their participation in multiprotein heterocomplexes has become apparent. In the present review, we discuss the structure and phosphorylation of GCKIIIs and then focus on their interactions with other proteins. GCKIIIs possess a highly-conserved, structured catalytic domain at the N-terminus and a less-well conserved C-terminal regulatory domain. GCKIIIs are activated by tonic autophosphorylation of a T-loop threonine residue and their phosphorylation is regulated primarily through protein serine/threonine phosphatases [especially PP2A (protein phosphatase 2A)]. The GCKIII regulatory domains are highly disorganized, but can interact with more structured proteins, particularly the CCM3 (cerebral cavernous malformation 3)/PDCD10 (programmed cell death 10) protein. We explore the role(s) of GCKIIIs (and CCM3/PDCD10) in STRIPAK (striatin-interacting phosphatase and kinase) complexes and their association with the cis-Golgi protein GOLGA2 (golgin A2; GM130). Recently, an interaction of GCKIIIs with MO25 has been identified. This exhibits similarities to the STRADα (STE20-related kinase adaptor α)-MO25 interaction (as in the LKB1-STRADα-MO25 heterotrimer) and, at least for MST3, the interaction may be enhanced by cis-autophosphorylation of its regulatory domain. In these various heterocomplexes, GCKIIIs associate with the Golgi apparatus, the centrosome and the nucleus, as well as with focal adhesions and cell junctions, and are probably involved in cell migration, polarity and proliferation. Finally, we consider the association of GCKIIIs with a number of human diseases, particularly cerebral cavernous malformations.

The 2q37-deletion syndrome: an update of the clinical spectrum including overweight, brachydactyly and behavioural features in 14 new patients

The 2q37 locus is one of the most commonly deleted subtelomeric regions. Such a deletion has been identified in >100 patients by telomeric fluorescence in situ hybridization (FISH) analysis and, less frequently, by array-based comparative genomic hybridization (array-CGH). A recognizable '2q37-deletion syndrome' or Albright's hereditary osteodystrophy-like syndrome has been previously described. To better map the deletion and further refine this deletional syndrome, we formed a collaboration with the Association of French Language Cytogeneticists to collect 14 new intellectually deficient patients with a distal or interstitial 2q37 deletion characterized by FISH and array-CGH. Patients exhibited facial dysmorphism (13/14) and brachydactyly (10/14), associated with behavioural problems, autism or autism spectrum disorders of varying severity and overweight or obesity. The deletions in these 14 new patients measured from 2.6 to 8.8 Mb. Although the major role of HDAC4 has been demonstrated, the phenotypic involvement of several other genes in the deleted regions is unknown. We further refined the genotype-phenotype correlation for the 2q37 deletion. To do this, we examined the smallest overlapping deleted region for candidate genes for skeletal malformations (facial dysmorphism and brachydactyly), overweight, behavioural problems and seizures, using clinical data, a review of the literature, and the Manteia database. Among the candidate genes identified, we focus on the roles of PRLH, PER2, TWIST2, CAPN10, KIF1A, FARP2, D2HGDH and PDCD1.

The Human Obesity Gene Map: The 2003 Update

This is the tenth update of the human obesity gene map, incorporating published results up to the end of October 2003 and continuing the previous format. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, quantitative trait loci (QTLs) from human genome-wide scans and animal crossbreeding experiments, and association and linkage studies with candidate genes and other markers is reviewed. Transgenic and knockout murine models relevant to obesity are also incorporated (N = 55). As of October 2003, 41 Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. QTLs reported from animal models currently number 183. There are 208 human QTLs for obesity phenotypes from genome-wide scans and candidate regions in targeted studies. A total of 35 genomic regions harbor QTLs replicated among two to five studies. Attempts to relate DNA sequence variation in specific genes to obesity phenotypes continue to grow, with 272 studies reporting positive associations with 90 candidate genes. Fifteen such candidate genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, more than 430 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful sites can be found at http://obesitygene.pbrc.edu.

The Human Obesity Gene Map: The 2004 Update

This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.

Chromosome 2q37 deletion: clinical and molecular aspects

Terminal deletions of chromosome 2 with breakpoints at or within band 2q37, ranging from visible abnormalities to cryptic, subtelomeric deletions, have been recognized with increasing frequency among children with mild-moderate mental retardation, characteristic facial appearance, and behavioral manifestations which often place them on the autism spectrum. The stereotypic facial characteristics include prominent forehead, thin, highly arched eyebrows, depressed nasal bridge, full cheeks, deficient nasal alae and prominent columella, thin upper lip, and various minor anomalies of the pinnae. Abnormal nipples, including inverted nipples, have been reported in a number of cases. CNS, ocular, cardiac, gastrointestinal, renal, and other GU anomalies have been noted in nearly one-third of patients. Of note, coarctation or hypoplasia of the aorta has been described in several affected children. Wilms tumor, renal dysplasia, and tracheomalacia have been reported only with the most proximal breakpoint at band 2q37.1 while a range of GI anomalies, pyloric stenosis, and diaphragmatic defects have been reported with breakpoints throughout the region. A subset of patients with the most distal deletion present phenotypic features which mimic Albright hereditary osteodystrophy (AHO). In addition to the AHO-like phenotype, later onset findings include seizures and cystic kidneys. Timely diagnosis of this recognizable syndrome provides a basis for genetic counseling, appropriate surveillance, and intervention, and avoids unnecessary and expensive diagnostic testing.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.

Two new behavioral QTLs, Emo4 and Reb1, map to mouse Chromosome 1: Congenic strains and candidate gene identification studies

By use of newly developed subcongenic strains of mice from a parental B6.129-Il10-/- knockout/congenic strain, we have narrowed the critical region for a new behavioral QTL, called Emo4, for open-field activity to a segment of Chromosome 1 between Erbb4 (68.4Mb) and B3gnt7 (86.2 Mb). We have also uncovered an additional QTL governing repetitive beam breaks in the open field. This QTL, called Reb1, maps to the interval between Asb1 (91.4 Mb) and NM_172851 (100.0 Mb) and is one of the first QTLs mapped for this type of behavior. Genome-wide microarray expression analyses were then undertaken to help to identify candidate genes that may be the cause of these genetic differences in open-field performance. In this effort, we analyzed global gene expression differences in the amygdalae by use of Affymetrix GeneChips between B6, B6.129-Il10-/-, and B6.129R4. Several probe sets representing target Chr 1 genes were found that showed significantly differential expression in the subcongenic and congenic strains. Several candidate genes have been identified. One of these regions coincides with an homologous region in humans that has been associated with autism, a disease whose symptoms include repetitive actions. This study illustrates that the use of congenic strains combined with global gene expression analyses can produce a list of viable candidates. It further shows that caution should be observed when analyzing the effects of knockout/congenic strains because many of the gene expression differences in these comparisons could not be attributable to the ablated Il10 gene but rather to passenger gene effects.

Molecular delineation of deletions on 2q37.3 in three cases with an Albright hereditary osteodystrophy-like phenotype

A minority of the reported cases of terminal 2q37 deletion clinically resemble Albright hereditary osteodystrophy (AHO)/pseudopseudohypoparathyroidism and have only mild-to-moderate mental retardation. Our molecular and cytogenetic fluorescence in situ hybridization (FISH) findings on an additional three patients further reduce the size of the minimal critical region deleted in this syndrome to about 3 Mb. This region includes the G-protein-coupled receptor 35 (GPR35), glypican 1 (GPC1), and serine/threonine protein kinase 25 (STK25) genes on 2q37.3. We have further defined several polymorphic variants within the coding region and flanking regions of GPR35 gene, which could potentially be useful for rapid detection of GPR35 gene deletion. We postulate that the absence of GPR35 may, at least partly, account for the phenotypic resemblance to the AHO. We also believe that the deletion of GPR35 could be responsible for the entity brachydactyly mental retardation syndrome (OMIM #600430), which was coined based on the above minority of patients with terminal 2q37 deletion. We recommend that every patient with AHO phenotype should undergo 2q subtelomeric FISH screen and subsequently a molecular study on the GPR35 gene. GPC1 and/or STK25 haploinsufficiency may also contribute to the AHO-like phenotype.

Molecular cytogenetic analysis of five 2q37 deletions: refining the brachydactyly candidate region

Deletions of the 2q37 region are associated with a recognizable pattern of MCA/MR so-called the AHO-like syndrome. Brachydactyly is a variable but characteristic feature of this clinical entity. Here we report on five cases of cytogenetically visible de novo deletions of this 2q37 chromosome region. Using FISH, we characterized at the molecular level the breakpoints of these deletions using a set of 15 BACs, PACs and YACs. In four patients, terminal deletions of variable size ranged between 6.2 and 10 Mb. The fifth patient had an interstitial deletion with an AHO-like phenotype including brachydactyly. These findings when compared to previous observations allowed us to narrow down the brachydactyly critical region between BACs RP11-585E12 and RP11-351E10. It contains HDAC4 and STK25 candidate genes loci.

Chromosome 2q terminal deletion: report of 6 new patients and review of phenotype-breakpoint correlations in 66 individuals

We report a new patient with terminal deletion of chromosome 2 with breakpoint at 2q36 and five additional new patients with 2q terminal deletion with breakpoint at 2q37. Hemidiaphragmatic hernia is a novel finding in one patient with a breakpoint at 2q37.1. In comparing these patients to 60 previously reported individuals with 2q terminal deletions, certain physical abnormalities are loosely associated with positions of breakpoint. For example, facial features (e.g., prominent forehead, depressed nasal bridge, and dysmorphic ears and nose), short stature, and short hands and feet were frequent in patients with breakpoints at or proximal to 2q37.3. Reports of horseshoe kidney and Wilms tumor were limited to patients with a breakpoint at 2q37.1, and structural brain anomalies and tracheal anomalies were reported only in patients with breakpoints at or proximal to 2q37.1. Cleft palate was reported only in patients with the most proximal breakpoints (2q36 or 2q35). Neurological effects including developmental delay, mental retardation, autistic-like behavior, and hypotonia were typical in this patient population but did not stratify in severity according to breakpoint. Terminal deletion of the long arm of chromosome 2 should be considered in the infant with marked hypotonia, poor feeding, gastroesophageal reflux, and growth delay, and the older child with developmental delay, autistic behavior, and the characteristic facial and integumentary features described herein. Assignment of clinical features to specific breakpoints and refinement of predictive value may be useful in counseling.

Molecular characterization of a cryptic 2q37 deletion in a patient with Albright hereditary osteodystrophy-like phenotype

The Albright hereditary osteodystrophy-like (AHO-like) syndrome was recently defined as a rare dysmorphic syndrome including brachymetaphalangism and mental retardation. This phenotype occurs in Albright hereditary osteodystrophy (AHO) but unlike it, the level of the Gs alpha protein activity is not reduced. To date 59 patients with these clinical and biochemical features have been reported, and for the majority of them (57/59) a cytogenetically visible 2q37 deletion has been observed. We report a new case of typical AHO-like syndrome with normal karyotype. Using the polymorphic marker D2S125 we found a loss of heterozygosity suggestive of a de novo 2q37 deletion of maternal origin. This hypothesis was confirmed by FISH analysis with a subtelomeric 2q probe containing the D2S90 marker. Genotypic analysis allowed us to map the proximal breakpoint of the subtelomeric deletion within an interval delimited by D2S2338 (present) and D2S2253 (deleted). This 2q subtelomeric deletion as small as 4 Mb is to date the smallest one observed in association with a typical AHO-like phenotype, and allows us to move the centromeric boundary of the AHO-like critical region by 750 kb towards the 2q telomere.

Narrowing the candidate region of Albright hereditary osteodystrophy-like syndrome by deletion mapping in a patient with an unbalanced cryptic translocation t(2;6)(q37.3;q26)

We here describe a submicroscopic translocation affecting the subtelomeric regions of chromosomes 2q and 6q identified in a patient referred to us because of mental retardation, obesity, brachydactyly, and short stature. FISH analysis using subtelomeric probes showed a 46,XY,der(2)t(2;6)(q37.3;q26) in the propositus, and a balanced t(2;6) in his father and sister. FISH with region-specific genomic clones made it possible to map the 2q37.3 breakpoint precisely to the region covered by BAC 585E12, and the 6q26 breakpoint to between the regions encompassed by 414A5 and 480A20. The 2q subtelomeric deletion has often been found in patients with Albright hereditary osteodystrophy (AHO)-like syndrome but, to the best of our knowledge, the 2q37.3-qter monosomy ascertained in our patient is the smallest so far described within the syndrome's critical interval, and may thus enhance the search for the responsible genes.