No abstract

Growth retardation resulting in short stature is a major concern for parents and due to its great variety of causes, a complex diagnostic challenge for clinicians. A major locus involved in linear growth has been implicated within the pseudoautosomal region (PAR1) of the human sex chromosomes. We have determined an interval of 170 kb of DNA within PAR1 which was deleted in 36 individuals with short stature and different rearrangements on Xp22 or Yp11.3. This deletion was not detected in any of the relatives with normal stature or in a further 30 individuals with rearrangements on Xp22 or Yp11.3 with normal height. We have isolated a homeobox-containing gene (SHOX) from this region, which has at least two alternatively spliced forms, encoding proteins with different patterns of expression. We also identified one functionally significant SHOX mutation by screening 91 individuals with idiopathic short stature. Our data suggest an involvement of SHOX in idiopathic growth retardation and in the short stature phenotype of Turner syndrome patients.

SHANK genes code for scaffold proteins located at the post-synaptic density of glutamatergic synapses. In neurons, SHANK2 and SHANK3 have a positive effect on the induction and maturation of dendritic spines, whereas SHANK1 induces the enlargement of spine heads. Mutations in SHANK genes have been associated with autism spectrum disorders (ASD), but their prevalence and clinical relevance remain to be determined. Here, we performed a new screen and a meta-analysis of SHANK copy-number and coding-sequence variants in ASD. Copy-number variants were analyzed in 5,657 patients and 19,163 controls, coding-sequence variants were ascertained in 760 to 2,147 patients and 492 to 1,090 controls (depending on the gene), and, individuals carrying de novo or truncating SHANK mutations underwent an extensive clinical investigation. Copy-number variants and truncating mutations in SHANK genes were present in ∼1% of patients with ASD: mutations in SHANK1 were rare (0.04%) and present in males with normal IQ and autism; mutations in SHANK2 were present in 0.17% of patients with ASD and mild intellectual disability; mutations in SHANK3 were present in 0.69% of patients with ASD and up to 2.12% of the cases with moderate to profound intellectual disability. In summary, mutations of the SHANK genes were detected in the whole spectrum of autism with a gradient of severity in cognitive impairment. Given the rare frequency of SHANK1 and SHANK2 deleterious mutations, the clinical relevance of these genes remains to be ascertained. In contrast, the frequency and the penetrance of SHANK3 mutations in individuals with ASD and intellectual disability—more than 1 in 50—warrant its consideration for mutation screening in clinical practice.

N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the mammalian brain. Two glycine-binding NR1 subunits and two glutamate-binding NR2 subunits each form highly Ca²(+)-permeable cation channels which are blocked by extracellular Mg²(+) in a voltage-dependent manner. Either GRIN2B or GRIN2A, encoding the NMDA receptor subunits NR2B and NR2A, was found to be disrupted by chromosome translocation breakpoints in individuals with mental retardation and/or epilepsy. Sequencing of GRIN2B in 468 individuals with mental retardation revealed four de novo mutations: a frameshift, a missense and two splice-site mutations. In another cohort of 127 individuals with idiopathic epilepsy and/or mental retardation, we discovered a GRIN2A nonsense mutation in a three-generation family. In a girl with early-onset epileptic encephalopathy, we identified the de novo GRIN2A mutation c.1845C>A predicting the amino acid substitution p.N615K. Analysis of NR1-NR2A(N615K) (NR2A subunit with the p.N615K alteration) receptor currents revealed a loss of the Mg²(+) block and a decrease in Ca²(+) permeability. Our findings suggest that disturbances in the neuronal electrophysiological balance during development result in variable neurological phenotypes depending on which NR2 subunit of NMDA receptors is affected.

Using microarrays, we identified de novo copy number variations in the SHANK2 synaptic scaffolding gene in two unrelated individuals with autism-spectrum disorder (ASD) and mental retardation. DNA sequencing of SHANK2 in 396 individuals with ASD, 184 individuals with mental retardation and 659 unaffected individuals (controls) revealed additional variants that were specific to ASD and mental retardation cases, including a de novo nonsense mutation and seven rare inherited changes. Our findings further link common genes between ASD and intellectual disability.

Catecholaminergic signaling regulates various physiological functions, such as blood pressure 1 and is implicated in drug dependence, affective disorders and male aggressive behavior 2,3 . The actions of released catecholamines are terminated by sodium-driven, high-affinity transporters in the plasma membrane of the releasing neurons 4,5 and by a corticosteronesensitive, low-affinity, high-capacity extraneuronal transport system 6 , originally named uptake 2 , found in sympathetically innervated tissues 7 and in central nervous system glia 8 . Here we report the molecular identification and pharmacological characterization of the extraneuronal catecholamine transporter, which is unrelated to the family of sodium-driven neuronal monoamine transporters 5 .Extraneuronal uptake is closely related to the non-neuronal metabolism of catecholamines 7 by catechol-O-methyltransferase (COMT), which exists almost exclusively in non-neuronal cells 9 , and monoamine oxidases (MAO-A and MAO-B). Extraneuronal transport is the predominant pathway for terminating the actions of circulating adrenaline and noradrenaline 10 . Although neuronal and extraneuronal uptake compete for released catecholamines, these transport systems have distinct pharmacological profiles, that is, affinity for substrates and sensitivity to various drugs. Overlap in the antagonist sensitivity between extraneuronal catecholamine uptake and apical renal transport of organic cations by OCT2 (ref. 11) raised the possibility that the extraneuronal transporter might belong to the recently defined family of amphiphilic solute facilitators (ASF) 12 . Degenerate oligonucleotides were derived from common sequence motifs of the ASF family and used for PCR on cDNA from Caki-1 cells, a human kidney carcinoma cell line known to express extraneuronal noradrenaline transport 13 . Amplicons of the expected sizes were isolated by ultraviolet-protected gel electrophoresis, cloned and sequenced. A fragment with similarity to members of the ASF family was identified. This fragment, in northern analysis of Caki-1 mRNA, detected a single band with a length of approximately 3.4 kb. The full-length cDNA of the corresponding transporter was assembled from a Caki-1 cDNA library clone and a fragment from inverse PCR. Because of its functional characteristics, we named this new transporter EMT (extraneuronal transporter for monoamine transmitters).Amino-acid sequence analysis identified EMT as a new member of the ASF transporter family 12 . No proteins highly homologous to EMT are yet known. EMT is similar to the OCT and OAT proteins (renal transporters for organic cations and organic anions), with identity (similarity) scores of about 50% (70%) and 32% (55%), respectively. EMT consists of 556 amino acids ( Fig. 1) with 12 putative transmembrane segments. To determine whether the functional properties of EMT match the characteristics of extraneuronal transport of catecholamines, the EMT cDNA was inserted into the expression vector pcDNA3 and transfected into 293 cells, a cell line fro...

Background: Short stature affects approximately 2% of children, representing one of the more frequent disorders for which clinical attention is sought during childhood. Despite assumed genetic heterogeneity, mutations or deletions of the short stature homeobox-containing gene (SHOX) are found quite frequently in subjects with short stature. Haploinsufficiency of the SHOX gene causes short stature with highly variable clinical severity, ranging from isolated short stature without dysmorphic features to Léri-Weill syndrome, and with no functional copy of the SHOX gene, Langer syndrome. Methods: To characterise the clinical and molecular spectrum of SHOX deficiency in childhood we assessed the association between genotype and phenotype in a large cohort of children of short stature from 14 countries. Results: Screening of 1608 unrelated individuals with sporadic or familial short stature revealed SHOX mutations or deletions in 68 individuals (4.2%): complete deletions in 48 (70.6%), partial deletions in 4 (5.9%) and point mutations in 16 individuals (23.5%). Although mean height standard deviation score (SDS) was not different between participants of short stature with or without identified SHOX gene defects (-2.6 vs -2.6), detailed examination revealed that certain bone deformities and dysmorphic signs, such as short forearm and lower leg, cubitus valgus, Madelung deformity, high-arched palate and muscular hypertrophy, differed markedly between participants with or without SHOX gene defects (p,0.001). Phenotypic data were also compared for 33 children with Turner syndrome in whom haploinsufficiency of SHOX is thought to be responsible for the height deficit. Conclusion: A phenotype scoring system was developed that could assist in identifying the most appropriate subjects for SHOX testing. This study offers a detailed genotype-phenotype analysis in a large cohort of children of short stature, and provides quantitative clinical guidelines for testing of the SHOX gene.

Background-Identifying molecular pathways regulating the development of pacemaking and coordinated heartbeat is crucial for a comprehensive mechanistic understanding of arrhythmia-related diseases. Elucidation of these pathways has been complicated mainly by an insufficient definition of the developmental structures involved in these processes and the unavailability of animal models specifically targeting the relevant tissues. Here, we report on a highly restricted expression pattern of the homeodomain transcription factor Shox2 in the sinus venosus myocardium, including the sinoatrial nodal region and the venous valves. Methods and Results-To investigate its function in vivo, we have generated mouse lines carrying a targeted mutation of the Shox2 gene. Although heterozygous animals did not exhibit obvious defects, homozygosity of the targeted allele led to embryonic lethality at 11.5 to 13.5 dpc. Shox2 Ϫ/Ϫ embryos exhibited severe hypoplasia of the sinus venosus myocardium in the posterior heart field, including the sinoatrial nodal region and venous valves. We furthermore demonstrate aberrant expression of connexin 40 and connexin 43 and the transcription factor Nkx2.5 in vivo specifically within the sinoatrial nodal region and show that Shox2 deficiency interferes with pacemaking function in zebrafish embryos. Conclusions-From these results, we postulate a critical function of Shox2 in the recruitment of sinus venosus myocardium comprising the sinoatrial nodal region.