Mutations in the GLI3 zinc-finger transcription factor gene cause Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS), which are variable but distinct clinical entities. We hypothesized that GLI3 mutations that predict a truncated functional repressor protein cause PHS and that functional haploinsufficiency of GLI3 causes GCPS. To test these hypotheses, we screened patients with PHS and GCPS for GLI3 mutations. The patient group consisted of 135 individuals: 89 patients with GCPS and 46 patients with PHS. We detected 47 pathological mutations (among 60 probands); when these were combined with previously published mutations, two genotype-phenotype correlations were evident. First, GCPS was caused by many types of alterations, including translocations, large deletions, exonic deletions and duplications, small in-frame deletions, and missense, frameshift/nonsense, and splicing mutations. In contrast, PHS was caused only by frameshift/nonsense and splicing mutations. Second, among the frameshift/nonsense mutations, there was a clear genotype-phenotype correlation. Mutations in the first third of the gene (from open reading frame [ORF] nucleotides [nt] 1-1997) caused GCPS, and mutations in the second third of the gene (from ORF nt 1998-3481) caused primarily PHS. Surprisingly, there were 12 mutations in patients with GCPS in the 3' third of the gene (after ORF nt 3481), and no patients with PHS had mutations in this region. These results demonstrate a robust correlation of genotype and phenotype for GLI3 mutations and strongly support the hypothesis that these two allelic disorders have distinct modes of pathogenesis.

Background-Microdeletions within chromosome 15q13.3 are associated both with a recently recognised syndrome of mental retardation, seizures, and dysmorphic features, and with schizophrenia.

We describe the molecular and clinical characterization of nine individuals with recurrent, 3.4-Mb, de novo deletions of 3q13.2q13.31 detected by chromosomal microarray analysis. All individuals have hypotonia and language and motor delays and also variably express mild to moderate cognitive delays (8/9), abnormal behavior (7/9), and autism spectrum disorders (3/9). Common facial features include down-slanting palpebral fissures with epicanthal folds, a slightly bulbous nose, and relative macrocephaly. Twenty-eight genes map to the deleted region, including four strong candidate genes, DRD3, ZBTB20, GAP43, and BOC, with important roles in neural and/or muscular development. Analysis of the breakpoint regions based on array data revealed directly oriented human endogenous retrovirus (HERV-H) elements ∼5kb in size and of >95% DNA sequence identity flanking the deletion. Subsequent DNA sequencing revealed different deletion breakpoints and suggested non-allelic homologous recombination (NAHR) between HERV-H elements as a mechanism of deletion formation, analogous to HERV-I-flanked and NAHR-mediated AZFa deletions. We propose that similar HERV elements may also mediate other recurrent deletion and duplication events on a genome-wide scale. Observation of rare recurrent chromosomal events such as these deletions helps to further the understanding of mechanisms behind naturally occurring variation in the human genome and its contribution to genetic disease.

There are limited data on the longitudinal frequency and severity of the symptoms and complications of achondroplasia. We undertook a retrospective electronic chart review of 114 patients to develop a more thorough understanding of the lifetime impact of achondroplasia. Craniocervical stenosis (involving the foramen magnum with or without cervical vertebrae C1 and/or C2) was noted in nearly 50% of patients with craniovertebral junction imaging; however, corrective decompression surgery was only needed in 6% of patients. No children in our cohort died at 4 years of age or under. Kyphosis was present in most patients but usually resolved in early childhood. Cervical and lumbar stenosis were diagnosed in children and adults while, genu varum, elbow contractures, and radial head dislocations were identified during childhood. Central sleep apnea and obstructive sleep apnea were present in children, while the diagnosis of obstructive sleep apnea was shown to recur in adulthood. Cardiovascular risk factors were present in only 7% of patients. A range of mental health disorders were identified, with most diagnoses being made before 18 years of age. Our data show that achondroplasia has a significant impact on patients' physical health, and complications continue to be reported and require intervention throughout patients' lifetimes. This highlights the need for continuous support beyond pediatric care, by adult care clinicians experienced with managing the long-term complications of achondroplasia.

Background We aimed to define the clinical and variant spectrum and to provide novel molecular insights into the DHX30-associated neurodevelopmental disorder. Methods Clinical and genetic data from affected individuals were collected through Facebook-based family support group, GeneMatcher, and our network of collaborators. We investigated the impact of novel missense variants with respect to ATPase and helicase activity, stress granule (SG) formation, global translation, and their effect on embryonic development in zebrafish. SG formation was additionally analyzed in CRISPR/Cas9-mediated DHX30-deficient HEK293T and zebrafish models, along with in vivo behavioral assays. Results We identified 25 previously unreported individuals, ten of whom carry novel variants, two of which are recurrent, and provide evidence of gonadal mosaicism in one family. All 19 individuals harboring heterozygous missense variants within helicase core motifs (HCMs) have global developmental delay, intellectual disability, severe speech impairment, and gait abnormalities. These variants impair the ATPase and helicase activity of DHX30, trigger SG formation, interfere with global translation, and cause developmental defects in a zebrafish model. Notably, 4 individuals harboring heterozygous variants resulting either in haploinsufficiency or truncated proteins presented with a milder clinical course, similar to an individual harboring a de novo mosaic HCM missense variant. Functionally, we established DHX30 as an ATP-dependent RNA helicase and as an evolutionary conserved factor in SG assembly. Based on the clinical course, the variant location, and type we establish two distinct clinical subtypes. DHX30 loss-of-function variants cause a milder phenotype whereas a severe phenotype is caused by HCM missense variants that, in addition to the loss of ATPase and helicase activity, lead to a detrimental gain-of-function with respect to SG formation. Behavioral characterization of dhx30-deficient zebrafish revealed altered sleep-wake activity and social interaction, partially resembling the human phenotype. Conclusions Our study highlights the usefulness of social media to define novel Mendelian disorders and exemplifies how functional analyses accompanied by clinical and genetic findings can define clinically distinct subtypes for ultra-rare disorders. Such approaches require close interdisciplinary collaboration between families/legal representatives of the affected individuals, clinicians, molecular genetics diagnostic laboratories, and research laboratories.