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The combination of skull defects in the form of enlarged parietal foramina (PFM) and deficient ossification of the clavicles is known as parietal foramina with cleidocranial dysplasia (PFMCCD). It is considered to be distinct from classical cleidocranial dysplasia (CCD) and is listed as a separate OMIM entry (168550). So far, only two families have been reported and the molecular basis of the disorder is unknown. We present a third family with PFMCCD, comprising four affected individuals in three generations, and demonstrate that a heterozygous tetranucleotide duplication in the MSX2 homeobox gene (505_508dupATTG) segregates with the phenotype. PFMCCD is indeed aetiologically distinct from CCD, which is caused by mutations in the RUNX2 gene, but allelic with isolated PFM, in which MSX2 mutations were previously identified. Our observations highlight the role of MSX2 in clavicular development and the importance of radiological examination of the clavicles in subjects with PFM

Mutations in the nuclear localization sequence of the Aristaless related homeobox; sequestration of mutant ARX with IPO13 disrupts normal subcellular distribution of the transcription factor and retards cell division

The electronic version of this article is the complete one and can be found online at: http://www.pathogeneticsjournal.com/content/3/1/1Background: Aristaless related homeobox (ARX) is a paired-type homeobox gene. ARX function is frequently affected by naturally occurring mutations. Nonsense mutations, polyalanine tract expansions and missense mutations in ARX cause a range of intellectual disability and epilepsy phenotypes with or without additional features including hand dystonia, lissencephaly, autism or dysarthria. Severe malformation phenotypes, such as X-linked lissencephaly with ambiguous genitalia (XLAG), are frequently observed in individuals with protein truncating or missense mutations clustered in the highly conserved paired-type homeodomain. Results: We have identified two novel point mutations in the R379 residue of the ARX homeodomain; c.1135C>A, p.R379S in a patient with infantile spasms and intellectual disability and c.1136G>T, p.R379L in a patient with XLAG. We investigated these and other missense mutations (R332P, R332H, R332C, T333N: associated with XLAG and Proud syndrome) predicted to affect the nuclear localisation sequences (NLS) flanking either end of the ARX homeodomain. The NLS regions are required for correct nuclear import facilitated by Importin 13 (IPO13). We demonstrate that missense mutations in either the N- or C-terminal NLS regions of the homeodomain cause significant disruption to nuclear localisation of the ARX protein in vitro. Surprisingly, none of these mutations abolished the binding of ARX to IPO13. This was confirmed by co-immunoprecipitation and immmuno fluorescence studies. Instead, tagged and endogenous IPO13 remained bound to the mutant ARX proteins, even in the RanGTP rich nuclear environment. We also identify the microtubule protein TUBA1A as a novel interacting protein for ARX and show cells expressing mutant ARX protein accumulate in mitosis, indicating normal cell division may be disrupted. Conclusions: We show that the most likely, common pathogenic mechanism of the missense mutations in NLS regions of the ARX homeodomain is inadequate accumulation and distribution of the ARX transcription factor within the nucleus due to sequestration of ARX with IPO13.Cheryl Shoubridge, May Huey Tan, Tod Fullston, Desiree Cloosterman, David Coman, George McGillivray, Grazia M Mancini, Tjitske Kleefstra and Jozef Géc

Enlarged parietal foramina

CLINICAL CHARACTERISTICS: Enlarged parietal foramina are characteristic symmetric, paired radiolucencies of the parietal bones, located close to the intersection of the sagittal and lambdoid sutures, caused by deficient ossification around the parietal notch, which is normally obliterated by the fifth month of fetal development. Enlarged parietal foramina are usually asymptomatic. Meningeal, cortical, and vascular malformations of the posterior fossa occasionally accompany the bone defects and may predispose to epilepsy. In a minority of individuals, headaches, vomiting, or intense local pain are sometimes associated with the defects, especially on application of mild pressure to the unprotected cerebral cortex. DIAGNOSIS/TESTING: Typically oval or round, enlarged parietal foramina resemble a "pair of spectacles" on postero-anterior skull radiographs. They may be less apparent on lateral skull radiographs because the lucencies are projected obliquely through normal bone. In young children, the disorder may present as a persistently enlarged posterior fontanelle caused by a single large central parietal bone defect (cranium bifidum). 3D CT scanning using bone windows clearly reveals the defect. MRI is useful in defining associated intracranial anatomic changes. Heterozygous pathogenic variants in either ALX4 or MSX2 are established causes. MANAGEMENT: Treatment of manifestations: Treatment is generally conservative. Persistent cranium bifidum may warrant operative closure. Associated headaches or seizures should be treated appropriately. The risk for penetrating injury to the brain is small but may cause anxiety; education of parents, teachers, and the affected child to avoid risky behaviors that could result in injury suffices in most circumstances. Agents/circumstances to avoid: Contact sports in those with a persistent midline bony defect. GENETIC COUNSELING: Enlarged parietal foramina are inherited in an autosomal dominant manner with high, but not complete, penetrance. Most individuals diagnosed with enlarged parietal foramina have an affected parent. The proportion of cases caused by de novo pathogenic variants appears to be small. Each child of an individual with enlarged parietal foramina has a 50% chance of inheriting the pathogenic variant. Detailed fetal ultrasound examination at 18 to 20 weeks' gestation can usually detect the defects in a fetus at risk; fetal MRI is also an option. When the pathogenic variant has been identified in an affected family member, prenatal diagnosis of a pregnancy at increased risk and preimplantation genetic testing are possible.</p

Enlarged parietal foramina

CLINICAL CHARACTERISTICS: Enlarged parietal foramina are characteristic symmetric, paired radiolucencies of the parietal bones, located close to the intersection of the sagittal and lambdoid sutures, caused by deficient ossification around the parietal notch, which is normally obliterated by the fifth month of fetal development. Enlarged parietal foramina are usually asymptomatic. Meningeal, cortical, and vascular malformations of the posterior fossa occasionally accompany the bone defects and may predispose to epilepsy. In a minority of individuals, headaches, vomiting, or intense local pain are sometimes associated with the defects, especially on application of mild pressure to the unprotected cerebral cortex. DIAGNOSIS/TESTING: Typically oval or round, enlarged parietal foramina resemble a "pair of spectacles" on postero-anterior skull radiographs. They may be less apparent on lateral skull radiographs because the lucencies are projected obliquely through normal bone. In young children, the disorder may present as a persistently enlarged posterior fontanelle caused by a single large central parietal bone defect (cranium bifidum). 3D CT scanning using bone windows clearly reveals the defect. MRI is useful in defining associated intracranial anatomic changes. Heterozygous pathogenic variants in either ALX4 or MSX2 are established causes. MANAGEMENT: Treatment of manifestations: Treatment is generally conservative. Persistent cranium bifidum may warrant operative closure. Associated headaches or seizures should be treated appropriately. The risk for penetrating injury to the brain is small but may cause anxiety; education of parents, teachers, and the affected child to avoid risky behaviors that could result in injury suffices in most circumstances. Agents/circumstances to avoid: Contact sports in those with a persistent midline bony defect. GENETIC COUNSELING: Enlarged parietal foramina are inherited in an autosomal dominant manner with high, but not complete, penetrance. Most individuals diagnosed with enlarged parietal foramina have an affected parent. The proportion of cases caused by de novo pathogenic variants appears to be small. Each child of an individual with enlarged parietal foramina has a 50% chance of inheriting the pathogenic variant. Detailed fetal ultrasound examination at 18 to 20 weeks' gestation can usually detect the defects in a fetus at risk; fetal MRI is also an option. When the pathogenic variant has been identified in an affected family member, prenatal diagnosis of a pregnancy at increased risk and preimplantation genetic testing are possible.</p

Enlarged parietal foramina caused by mutations in the homeobox genes ALX4 and MSX2: from genotype to phenotype.

Heterozygous mutations of the homeobox genes ALX4 and MSX2 cause skull defects termed enlarged parietal foramina (PFM) and cranium bifidum (CB); a single MSX2 mutation has been documented in a unique craniosynostosis (CRS) family. However, the relative mutational contribution of these genes to PFM/CB and CRS is not known and information on genotype-phenotype correlations is incomplete. We analysed ALX4 and MSX2 in 11 new unrelated cases or families with PFM/CB, 181 cases of CRS, and a single family segregating a submicroscopic deletion of 11p11.2, including ALX4. We explored the correlations between skull defect size and age, gene, and mutation type, and reviewed additional phenotypic manifestations. Four PFM cases had mutations in either ALX4 or MSX2; including previous families, we have identified six ALX4 and six MSX2 mutations, accounting for 11/13 familial, but only 1/6 sporadic cases. The deletion family confirms the delineation of a mental retardation locus to within 1.1 Mb region of 11p11.2. Overall, no significant size difference was found between ALX4- and MSX2-related skull defects, but the ALX4 mutation p.R218Q tends to result in persistent CB and is associated with anatomical abnormalities of the posterior fossa. We conclude that PFM caused by mutations in ALX4 and MSX2 have a similar prevalence and are usually clinically indistinguishable. Mutation screening has a high pickup rate in PFM, especially in familial cases, but is not indicated in CRS

Quantitation of X-Y homologous genes in patients with schizophrenia by multiplex polymerase chain reaction.

OBJECTIVES: The genetic basis of schizophrenia is obscure. In an XX male patient with schizophrenia we previously showed that one X;Y translocation breakpoint was in pseudoautosomal region 1 (PAR1) with the effect that the proximal segment of PAR1 from the PAR1 boundary to acetylserotonin N-methyl transferase (ASMT) distally was triplicated in this patient. This study determined whether dosage imbalances of X-Y homologous regions in general are associated with schizophrenia. METHODS: A multiplex semi-quantitative polymerase chain reaction assay was developed to quantify MIC2 gene as a representative of PAR1 and compare it with the SYBL1 gene which maps in pseudoautosomal region 2 (PAR2) and protocadherin XY (PCDHXY), located at Xq21.3. Each of these three loci was co-amplified with the autosomal gene MSX2 using Cy5-labelled primers and the products separated by electrophoresis in polyacrylamide gels. Results were expressed as ratios of peak area of the target gene to MSX2 which served as an internal dosage control. RESULTS: Using genomes with sex chromosome aneuploidies, the method was found sensitive enough to detect a two-fold difference in gene copy number. We confirmed the MIC2 triplication in the XX male patient but found no significant difference in gene dosage of MIC2, PCDHXY and SYBL1 in a panel of 17 patients with schizophrenia compared to controls. CONCLUSIONS: No evidence was obtained for gene dosage imbalances in MIC2, PCDHXY and SYBL1 in patients with schizophrenia