A recognizable type of syndromic short stature with arthrogryposis caused by bi-allelic SEMA3A loss-of-function variants

Expanding the Phenotype of the FAM149B1-Related Ciliopathy and Identification of Three Neurogenetic Disorders in a Single Family

Biallelic truncating FAM149B1 variants result in cilia dysfunction and have been reported in four infants with Joubert syndrome and orofaciodigital syndrome type VI, respectively. We report here on three adult siblings, 18 to 40 years of age, homozygous for the known FAM149B1 c.354_357delinsCACTC (p.Gln118Hisfs*20) variant. Detailed clinical examinations were performed including ocular and gait analyses, skeletal- and neuroimaging. All three patients presented with neurological and oculomotor symptoms since birth and mild skeletal dysplasia in infancy resulting in characteristic gait abnormalities. We document mild skeletal dysplasia, abnormal gait with increased hip rotation and increased external foot rotation, ataxia, variable polydactyly, ocular Duane syndrome, progressive ophthalmoplegia, nystagmus, situs inversus of the retinal vessels, olfactory bulb aplasia, and corpus callosal dysgenesis as novel features in FAM149B1-ciliopathy. We show that intellectual disability is mild to moderate and retinal, renal and liver function is normal in these affected adults. Our study thus expands the FAM149B1-related Joubert syndrome to a mainly neurological and skeletal ciliopathy phenotype with predominant oculomotor dysfunction but otherwise stable outcome in adults. Diagnosis of FAM149B1-related disorder was impeded by segregation of multiple neurogenetic disorders in the same family, highlighting the importance of extended clinical and genetic studies in families with complex phenotypes.

Characteristic facial features and cortical blindness distinguish the DOCK7-related epileptic encephalopathy

Background

The epileptic encephalopathies display extensive locus and allelic heterogeneity. Biallelic truncating DOCK7 variants were recently reported in five children with early‐onset epilepsy, intellectual disability, and cortical blindness, indicating that DOCK7 deficiency causes a specific type of epileptic encephalopathy.

Methods

We identified 23‐ and 27‐year‐old siblings with the clinical pattern reported for DOCK7 deficiency, and conducted genome‐wide linkage analysis and WES. The consequences of a DOCK7 variant were analyzed on the transcript and protein level in patients’ fibroblasts.

Results

We identified a novel homozygous DOCK7 frameshift variant, an intragenic tandem duplication of 124‐kb, previously missed by CGH array, in adult patients. Patients display atrophy in the occipital lobe and pontine hypoplasia with marked pontobulbar sulcus, and focal atrophy of occasional cerebellar folia is a novel finding. Recognizable dysmorphic features include normo‐brachycephaly, narrow forehead, low anterior and posterior hairlines, prominent ears, full cheeks, and long eyelashes. Our patients function on the level of 4‐year‐old children, never showed signs of regression, and seizures are largely controlled with multi‐pharmacotherapy. Studies of patients’ fibroblasts showed nonsense‐mediated RNA decay and lack of DOCK7 protein.

Conclusion

DOCK7 deficiency causes a definable clinical entity, a recognizable type of epileptic encephalopathy.

Kallmann syndrome and idiopathic hypogonadotropic hypogonadism: The role of semaphorin signaling on GnRH neurons

Idiopathic hypogonadotropic hypogonadism and Kallmann syndrome are rare genetic disorders characterized by isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) and delayed or absent puberty. Defective GnRH neuron migration during development or secretion of mature GnRH neurons secondary to molecular defects in several key developmental and neuroendocrine pathways are thought to be the primary causes of these disorders. Recent studies have highlighted the importance of semaphorins and their receptors in this system, by showing that these molecules play distinct roles during the development and plasticity of these neurons. Accordingly, mutations in the semaphoring-signaling pathway genes have been found in patients affected by IGD, underlying the importance of semaphorin-mediated signaling pathways in the neuroendocrine axis that control reproduction.

Further delineation of a recognizable type of syndromic short stature caused by biallelic SEMA3A loss-of-function variants

The semaphorin protein family is a diverse set of extracellular signaling proteins that perform fundamental roles in the development and operation of numerous biological systems, notably the nervous, musculoskeletal, cardiovascular, endocrine, and reproductive systems. Recently, recessive loss-of-function (LoF) variants in SEMA3A (semaphorin 3A) have been shown to result in a recognizable syndrome characterized by short stature, skeletal abnormalities, congenital heart defects, and variable additional anomalies. Here, we describe the clinical and molecular characterization of a female patient presenting with skeletal dysplasia, hypogonadotropic hypogonadism (HH), and anosmia who harbors a nonsense variant c.1633C>T (p.Arg555*) and a deletion of exons 15, 16, and 17 in SEMA3A in the compound heterozygous state. These variants were identified through next-generation sequencing analysis of a panel of 26 genes known to be associated with HH/Kallmann syndrome. Our findings further substantiate the notion that biallelic LoF SEMA3A variants cause a syndromic form of short stature and expand the phenotypic spectrum associated with this condition to include features of Kallmann syndrome.

Further delineation of putative ACTB loss-of-function variants: A 4-patient series

ACTB encodes β‐cytoplasmic actin, an essential component of the cytoskeleton. Based on chromosome 7p22.1 deletions that include the ACTB locus and on rare truncating ACTB variants, a phenotype resulting from ACTB haploinsufficiency was recently proposed. We report putative ACTB loss‐of‐function variants in four patients. To the best of our knowledge, we report the first 7p22.1 microdeletion confined to ACTB and the second ACTB frameshifting mutation that predicts mRNA decay. A de‐novo ACTB p.(Gly302Ala) mutation affects β‐cytoplasmic actin distribution. All four patients share a facial gestalt that is distinct from that of individuals with dominant‐negative ACTB variants in Baraitser‐Winter cerebrofrontofacial syndrome. Two of our patients had strikingly thin and sparse scalp hair. One patient had sagittal craniosynostosis and hypospadias. All three affected male children have attention deficits and mild global developmental delay. Mild intellectual disability was present in only one patient. Heterozygous ACTB deletion can allow for normal psychomotor function.

Recognizable type of pituitary, heart, kidney and skeletal dysplasia mostly caused by SEMA3A mutation: A case report

BACKGROUND

The SEMA3A gene, which is located at 7q21.11, is involved in hypothalamic neuron migration, heart development, kidney development, and skeleton metabolism. Mutation of the SEMA3A gene is associated with Kallmann syndrome 16 with or without a normal sense of smell. In addition, two case reports showed that mutation of the SEMA3A gene could cause short stature, low gonadotropin, hypogonadism, thoracic deformity, a high scapula, rib and lower limb deformity, facial deformity (long face, epicanthic folds, backwards ears), and arterial malformation.

CASE SUMMARY

We reported the case of a 26-year-old Chinese man who was admitted because of short stature. Physical examination showed that he had many abnormal symptoms, including a short neck, facial moles, knee valgus, transverse palm, continuous grade 5/6 murmurs in the pulmonary auscultation area, no whiskers, or pubic hair, no Adam’s apple, short penis and cryptorchidism. Radiological examination showed pituitary, gonad, heart, kidney and skeletal dysplasia. The laboratory tests revealed low growth hormone, luteinizing hormone, follicle-stimulating hormone, testosterone and estrogen. Clinical whole-exome detection showed that our patient, unlike previously reported patients, has a new SEMA3A gene mutation (c.950A>G). Now, his height has increased by 3 cm. In addition, he has a good appetite and reduced subcutaneous fat over 3 mo of recombinant human growth hormone injections therapy. Unfortunately, he refuses further treatment about gonad.

CONCLUSION

Patients who come to a hospital because of their short stature must undergo gene detection if they have other simultaneous abnormal phenotypes.