CHEDDA syndrome is an underrecognized neurodevelopmental disorder with a highly restricted ATN1 mutation spectrum.

We describe the clinical features of nine unrelated individuals with rare de novo missense or in-frame deletions/duplications within the "HX motif" of exon 7 of ATN1. We previously proposed that individuals with such variants should be considered as being affected by the syndromic condition of congenital hypotonia, epilepsy, developmental delay, and digital anomalies (CHEDDA), distinct from dentatorubral-pallidoluysian atrophy (DRPLA) secondary to expansion variants in exon 5 of ATN1. We confirm that the universal phenotypic features of CHEDDA are distinctive facial features and global developmental delay. Infantile hypotonia and minor hand and feet differences are common and can present as arthrogryposis. Common comorbidities include severe feeding difficulties, often requiring gastrostomy support, as well as visual and hearing impairments. Epilepsy and congenital malformations of the brain, heart, and genitourinary systems are frequent but not universal. Our study confirms the clinical entity of CHEDDA secondary to a mutational signature restricted to exon 7 of ATN1. We propose a clinical schedule for assessment upon diagnosis, surveillance, and early intervention including the potential of neuroimaging for prognostication.

Genetic Counseling for Neurofibromatosis 1, Neurofibromatosis 2, and Schwannomatosis-Practice Resource of the National Society of Genetic Counselors.

The goal of this practice resource is to provide genetic counselors and other healthcare professionals with a resource to reference when providing genetic counseling services to individuals and families undergoing evaluation for neurofibromatosis (NF) or who have received a diagnosis of NF, including NF1, NF2, and schwannomatosis. This resource represents the opinions of a multi-center working group of Certified Genetic Counselors with experience in the care of individuals with NF, providing topics to be considered for the incorporation into a clinical genetic counseling session.

A recurrent 8 bp frameshifting indel in FOXF1 defines a novel mutation hotspot associated with alveolar capillary dysplasia with misalignment of pulmonary veins.

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal lung developmental disease. Affected infants manifest with severe respiratory distress and refractory pulmonary hypertension and uniformly die in the first month of life. Heterozygous point mutations or copy-number variant deletions involving FOXF1 and/or its upstream lung-specific enhancer on 16q24.1 have been identified in the vast majority of ACDMPV patients. We have previously described two unrelated families with a de novo pathogenic frameshift variant c.691_698del (p.Ala231Argfs*61) in the exon 1 of FOXF1. Here, we present a third unrelated ACDMPV family with the same de novo variant and propose that a direct tandem repeat of eight consecutive nucleotides GCGGCGGC within the ~4 kb CpG island in FOXF1 exon 1 is a novel mutation hotspot causative for ACDMPV.

Mutations in SPATA5 Are Associated with Microcephaly, Intellectual Disability, Seizures, and Hearing Loss.

Using whole-exome sequencing, we have identified in ten families 14 individuals with microcephaly, developmental delay, intellectual disability, hypotonia, spasticity, seizures, sensorineural hearing loss, cortical visual impairment, and rare autosomal-recessive predicted pathogenic variants in spermatogenesis-associated protein 5 (SPATA5). SPATA5 encodes a ubiquitously expressed member of the ATPase associated with diverse activities (AAA) protein family and is involved in mitochondrial morphogenesis during early spermatogenesis. It might also play a role in post-translational modification during cell differentiation in neuronal development. Mutations in SPATA5 might affect brain development and function, resulting in microcephaly, developmental delay, and intellectual disability.

Novel pathogenic COX20 variants causing dysarthria, ataxia, and sensory neuropathy.

COX20/FAM36A encodes a mitochondrial complex IV assembly factor important for COX2 activation. Only one homozygous COX20 missense mutation has been previously described in two separate consanguineous families. We report four subjects with features that include childhood hypotonia, areflexia, ataxia, dysarthria, dystonia, and sensory neuropathy. Exome sequencing in all four subjects identified the same novel COX20 variants. One variant affected the splice donor site of intron-one (c.41A>G), while the other variant (c.157+3G>C) affected the splice donor site of intron-two. cDNA and protein analysis indicated that no full-length cDNA or protein was generated. These subjects expand the phenotype associated with COX20 deficiency.

A porcine model of neurofibromatosis type 1 that mimics the human disease.

Loss of the NF1 tumor suppressor gene causes the autosomal dominant condition, neurofibromatosis type 1 (NF1). Children and adults with NF1 suffer from pathologies including benign and malignant tumors to cognitive deficits, seizures, growth abnormalities, and peripheral neuropathies. NF1 encodes neurofibromin, a Ras-GTPase activating protein, and NF1 mutations result in hyperactivated Ras signaling in patients. Existing NF1 mutant mice mimic individual aspects of NF1, but none comprehensively models the disease. We describe a potentially novel Yucatan miniswine model bearing a heterozygotic mutation in NF1 (exon 42 deletion) orthologous to a mutation found in NF1 patients. NF1+/ex42del miniswine phenocopy the wide range of manifestations seen in NF1 patients, including café au lait spots, neurofibromas, axillary freckling, and neurological defects in learning and memory. Molecular analyses verified reduced neurofibromin expression in swine NF1+/ex42del fibroblasts, as well as hyperactivation of Ras, as measured by increased expression of its downstream effectors, phosphorylated ERK1/2, SIAH, and the checkpoint regulators p53 and p21. Consistent with altered pain signaling in NF1, dysregulation of calcium and sodium channels was observed in dorsal root ganglia expressing mutant NF1. Thus, these NF1+/ex42del miniswine recapitulate the disease and provide a unique, much-needed tool to advance the study and treatment of NF1.

Uniparental Isodisomy of Chromosome 1 Unmasking an Autosomal Recessive 3-Beta Hydroxysteroid Dehydrogenase Type II-Related Congenital Adrenal Hyperplasia.

Steroid 3-beta hydroxysteroid dehydrogenase type II (3ß-HSD2) deficiency is a rare autosomal recessive form of congenital adrenal hyperplasia (CAH). We report the genetic basis of 3ß-HSD2 deficiency arising from uniparental isodisomy (UPD) of chromosome 1. We describe a term undervirilized male whose newborn screen indicated borderline CAH. The patient presented on the 7th day of life in salt-wasting adrenal crisis. Steroid hormone testing revealed a complex pattern suggestive of 3ß-HSD deficiency. Chromosomal microarray and single nucleotide polymorphism analysis revealed complete UPD of chromosome 1. Sanger sequencing of HSD3B2 revealed a previously described missense mutation, c.424G>A (p.E142K) in homozygous state, thus confirming the diagnosis of 3ß-HSD2 deficiency. We provide evidence of the existence of an uncommon mechanism for HSD3B2 gene-related CAH arising from UPD of chromosome 1.