Premature Ovarian Insufficiency in CLPB Deficiency: Transcriptomic, Proteomic and Phenotypic Insights

CONTEXT

Premature ovarian insufficiency (POI) is a common form of female infertility that usually presents as an isolated condition but can be part of various genetic syndromes. Early diagnosis and treatment of POI can minimize comorbidity and improve health outcomes.

OBJECTIVE

We aimed to determine the genetic cause of syndromic POI, intellectual disability, neutropenia, and cataracts.

METHODS

We performed whole-exome sequencing (WES) followed by functional validation via RT-PCR, RNAseq, and quantitative proteomics, as well as clinical update of previously reported patients with variants in the caseinolytic peptidase B (CLPB) gene.

RESULTS

We identified causative variants in CLPB, encoding a mitochondrial disaggregase. Variants in this gene are known to cause an autosomal recessive syndrome involving 3-methylglutaconic aciduria, neurological dysfunction, cataracts, and neutropenia that is often fatal in childhood; however, there is likely a reporting bias toward severe cases. Using RNAseq and quantitative proteomics we validated causation and gained insight into genotype:phenotype correlation. Clinical follow-up of patients with CLPB deficiency who survived to adulthood identified POI and infertility as a common postpubertal ailment.

CONCLUSION

A novel splicing variant is associated with CLPB deficiency in an individual who survived to adulthood. POI is a common feature of postpubertal female individuals with CLPB deficiency. Patients with CLPB deficiency should be referred to pediatric gynecologists/endocrinologists for prompt POI diagnosis and hormone replacement therapy to minimize associated comorbidities.

Expression and Purification of Recombinant Skd3 (Human ClpB) Protein and Tobacco Etch Virus (TEV) Protease from Escherichia coli

Skd3 (encoded by human CLPB) is a mitochondrial AAA+ protein comprised of an N-terminal ankyrin-repeat domain and a C-terminal HCLR-clade nucleotide-binding domain. The function of Skd3 has long remained unknown due to challenges in purifying the protein to high quality and near homogeneity. Recently we described Skd3 as a human mitochondrial protein disaggregase that solubilizes proteins in the mitochondrial intermembrane space. This protocol overcomes the challenges associated with purifying Skd3 and allows for in depth in vitro study of Skd3 activity. Tobacco etch virus (TEV) protease is required in the purification of Skd3. Thus, we also describe how to purify high quality TEV protease for use in the purification of Skd3, other purification protocols, and in vitro assays requiring TEV protease.

Diagnosis and Management of Drooling in Children With Progressive Dystonia: A Case Series of Patients With MEGDEL Syndrome

Drooling is a common problem in children with progressive dystonia. The authors noted a 58% incidence of drooling in 22/38 children with MEGDEL, a rare neurodegenerative cause of dystonia and report on the clinical course of four patients. Drooling of varying severity and subsequent respiratory problems were treated at the authors' multidisciplinary saliva-control outpatient clinic. One patient improved on antireflux medication, the second after medication with drooling as side effect was changed. Two other patients underwent salivary gland surgery, one of whom significantly improved; the other died shortly after surgery. The heterogeneity of the cases presented shows the need for stepwise and personalized treatment. The authors recommend the following: (1) optimize the treatment of the underlying neurological condition and replace medication that stimulates saliva secretion; (2) treat constipation, scoliosis, and gastroesophageal reflux if there is still a risk of chronic aspiration of saliva; (3) perform more intense/invasive treatment (botulinum toxin, salivary gland surgery).