Biallelic PI4KA variants cause neurological, intestinal and immunological disease.

Phosphatidylinositol 4-kinase IIIα (PI4KIIIα/PI4KA/OMIM:600286) is a lipid kinase generating phosphatidylinositol 4-phosphate (PI4P), a membrane phospholipid with critical roles in the physiology of multiple cell types. PI4KIIIα's role in PI4P generation requires its assembly into a heterotetrameric complex with EFR3, TTC7 and FAM126. Sequence alterations in two of these molecular partners, TTC7 (encoded by TTC7A or TCC7B) and FAM126, have been associated with a heterogeneous group of either neurological (FAM126A) or intestinal and immunological (TTC7A) conditions. Here we show that biallelic PI4KA sequence alterations in humans are associated with neurological disease, in particular hypomyelinating leukodystrophy. In addition, affected individuals may present with inflammatory bowel disease, multiple intestinal atresia and combined immunodeficiency. Our cellular, biochemical and structural modelling studies indicate that PI4KA-associated phenotypical outcomes probably stem from impairment of PI4KIIIα-TTC7-FAM126's organ-specific functions, due to defective catalytic activity or altered intra-complex functional interactions. Together, these data define PI4KA gene alteration as a cause of a variable phenotypical spectrum and provide fundamental new insight into the combinatorial biology of the PI4KIIIα-FAM126-TTC7-EFR3 molecular complex.

Exome sequencing identifies a novel EP300 frame shift mutation in a patient with features that overlap Cornelia de Lange syndrome.

Rubinstein-Taybi syndrome (RTS) and Cornelia de Lange syndrome (CdLS) are genetically heterogeneous multiple anomalies syndromes, each having a distinctive facial gestalt. Two genes (CREBBP and EP300) are known to cause RTS, and five (NIPBL, SMC1A, SMC3, RAD21, and HDAC8) have been associated with CdLS. A diagnosis of RTS or CdLS is molecularly confirmed in only 65% of clinically identified cases, suggesting that additional causative genes exist for both conditions. In addition, although EP300 and CREBBP encode homologous proteins and perform similar functions, only eight EP300 positive RTS patients have been reported, suggesting that patients with EP300 mutations might be escaping clinical recognition. We report on a child with multiple congenital abnormalities and intellectual disability whose facial features and complex phenotype resemble CdLS. However, no mutations in CdLS-related genes were identified. Rather, a novel EP300 mutation was found on whole exome sequencing. Possible links between EP300 and genes causing CdLS are evident in the literature. Both EP300 and HDAC8 are involved in the regulation of TP53 transcriptional activity. In addition, p300 and other chromatin associated proteins, including NIPBL, SMCA1, and SMC3, have been found at enhancer regions in different cell types. It is therefore possible that EP300 and CdLS-related genes are involved in additional shared pathways, producing overlapping phenotypes. As whole exome sequencing becomes more widely utilized, the diverse phenotypes associated with EP300 mutations should be better understood. In the meantime, testing for EP300 mutations in those with features of CdLS may be warranted.

Intra-abdominal (Type IV) sacrococcygeal teratoma presenting with buttock hemangioma.

Sacrococcygeal teratoma is the most common type of extragonadal germ cell tumor in infants and young children. Sacrococcygeal teratomas can uncommonly present in an intra-abdominal fashion, with minimal clinical findings. Dermatologic lesions overlying the vertebrae or buttocks are often associated with sacrococcygeal teratoma and may be the only clue to their presence. Here, we report a case of an intra-abdominal sacrococcygeal teratoma presenting with an anatomically separate buttock hemangioma.

Homozygous mutation in SAMHD1 gene causes cerebral vasculopathy and early onset stroke.

We describe an autosomal recessive condition characterized with cerebral vasculopathy and early onset of stroke in 14 individuals in Old Order Amish. The phenotype of the condition was highly heterogeneous, ranging from severe developmental disability to normal schooling. Cerebral vasculopathy was a major hallmark of the condition with a common theme of multifocal stenoses and aneurysms in large arteries, accompanied by chronic ischemic changes, moyamoya morphology, and evidence of prior acute infarction and hemorrhage. Early signs of the disease included mild intrauterine growth restriction, infantile hypotonia, and irritability, followed by failure to thrive and short stature. Acrocyanosis, Raynaud's phenomenon, chilblain lesions, low-pitch hoarse voice, glaucoma, migraine headache, and arthritis were frequently observed. The early onset or recurrence of strokes secondary to cerebral vasculopathy seems to always be associated with poor outcomes. The elevated erythrocyte sedimentation rate (ESR), IgG, neopterin, and TNF-α found in these patients suggested an immune disorder. Through genomewide homozygosity mapping, we localized the disease gene to chromosome (Chr) 20q11.22-q12. Candidate gene sequencing identified a homozygous mutation, c.1411-2A > G, in the SAMHD1 gene, being associated with this condition. The mutation appeared at the splice-acceptor site of intron 12, resulted in the skipping of exon 13, and gave rise to an aberrant protein with in-frame deletion of 31 amino acids. Immunoblotting analysis showed lack of mutant SAMHD1 protein expression in affected cell lines. The function of SAMHD1 remains unclear, but the inflammatory vasculopathies of the brain found in the patients with SAMHD1 mutation indicate its important roles in immunoregulation and cerebral vascular hemeostasis.

Histologic and histochemical analysis of muscle specimens in idiopathic talipes equinovarus.

Congenital idiopathic talipes equinovarus is a relatively common disorder of uncertain etiology with a wide variance of clinical severity. Many theories have been postulated over the years without universal agreement in regard to the cause of this disorder. These hypotheses include vascular, viral, genetic, anatomic, compartment syndrome, environmental, and positioning considerations. A great deal of recent discussion has focused on a neuromuscular etiology for this condition. Muscle biopsies from the gastrocnemius, abductor hallucis, flexor digitorum longus, flexor hallucis, and tibialis posterior were obtained during posteromedial surgical release for idiopathic talipes equinovarus from September 1994 to October 2000 at the authors' institution. Ninety-five feet in 68 patients yielded a total of 431 muscle specimens. All of the specimens were processed and examined by light microscopy by an expert neuromuscular pathologist. In addition, 95 tissue samples were further processed for histochemical studies and electron microscopy. Three hundred seventy-two specimens (86.3%) showed no evidence of a pathologic diagnosis with normal fiber-type ratios and no type I fiber grouping indicative of neuromuscular pathology. Only 4 specimens (0.9%) showed type I fiber predominance, and 55 specimens (12.8%) revealed muscle fiber atrophy. The results of this study do not support the theory that a neuromuscular abnormality may be significant in the etiology of idiopathic talipes equinovarus.

Prenatal diagnosis of tetralogy of Fallot with obstructed supracardiac totally anomalous pulmonary venous connection.

We describe our experience with prenatal diagnosis of tetralogy of Fallot with supracardiac totally anomalous pulmonary venous connection. We also suspected obstruction in the ascending vertical vein as it crossed the right bronchus and coursed superiorly to join the right superior caval vein. This finding was confirmed on postnatal echocardiography, and at autopsy.