Improving diagnostic precision in primary ovarian insufficiency using comprehensive genetic and autoantibody testing.

STUDY QUESTION: Is it possible to find the cause of primary ovarian insufficiency (POI) in more women by extensive screening? SUMMARY ANSWER: Adding next generation sequencing techniques including a POI-associated gene panel, extended whole exome sequencing data, as well as specific autoantibody assays to the recommended diagnostic investigations increased the determination of a potential etiological diagnosis of POI from 11% to 41%. WHAT IS KNOWN ALREADY: POI affects ∼1% of women. Clinical presentations and pathogenic mechanisms are heterogeneous and include genetic, autoimmune, and environmental factors, but the underlying etiology remains unknown in the majority of cases. STUDY DESIGN, SIZE, DURATION: Prospective cross-sectional study of 100 women with newly diagnosed POI of unknown cause consecutively referred to Haukeland University Hospital, Bergen, Norway, January 2019 to December 2021. PARTICIPANTS/MATERIALS, SETTING, METHODS: In addition to standard recommended diagnostic investigations including screening for chromosomal anomalies and premutations in the fragile X mental retardation 1 gene (FMR1) we used whole exome sequencing, including targeted analysis of 103 ovarian-related genes, and assays of autoantibodies against steroid cell antigens. MAIN RESULTS AND THE ROLE OF CHANCE: We identified chromosomal aberrations in 8%, FMR1 premutations in 3%, genetic variants related to POI in 16%, and autoimmune POI in 3%. Furthermore in 11% we identified POI associated genetic Variants of unknown signifcance (VUS). A homozygous pathogenic variant in the ZSWIM7 gene (NM_001042697.2) was found in two women, corroborating this as a novel cause of monogenic POI. No associations between phenotypes and genotypes were found. LIMITATIONS, REASONS FOR CAUTION: Use of candidate genetic and autoimmune markers limit the possibility to discover new markers. To further investigate the genetic variants, family studies would have been useful. We found a relatively high proportion of genetic variants in women from Africa and lack of genetic diversity in the genomic databases can impact diagnostic accuracy. WIDER IMPLICATIONS OF THE FINDINGS: Since no specific clinical or biochemical markers predicted the underlying cause of POI discussion of which tests should be part of diagnostic screening in clinical practice remains open. New technology has altered the availability and effectiveness of genetic testing, and cost-effectiveness analyses are required to aid sustainable diagnostics. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by grants and fellowships from Stiftelsen Kristian Gerhard Jebsen, the Novonordisk Foundation, the Norwegian Research Council, University of Bergen, and the Regional Health Authorities of Western Norway. The authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: NCT04082169.

Clinical Cases and the Molecular Profiling of a Novel Childhood Encephalopathy-Causing GNAO1 Mutation P170R.

De novo mutations in GNAO1, the gene encoding the major neuronal G protein Gαo, cause a spectrum of pediatric encephalopathies with seizures, motor dysfunction, and developmental delay. Of the >80 distinct missense pathogenic variants, many appear to uniformly destabilize the guanine nucleotide handling of the mutant protein, speeding up GTP uptake and deactivating GTP hydrolysis. Zinc supplementation emerges as a promising treatment option for this disease, as Zn2+ ions reactivate the GTP hydrolysis on the mutant Gαo and restore cellular interactions for some of the mutants studied earlier. The molecular etiology of GNAO1 encephalopathies needs further elucidation as a prerequisite for the development of efficient therapeutic approaches. In this work, we combine clinical and medical genetics analysis of a novel GNAO1 mutation with an in-depth molecular dissection of the resultant protein variant. We identify two unrelated patients from Norway and France with a previously unknown mutation in GNAO1, c.509C>G that results in the production of the Pro170Arg mutant Gαo, leading to severe developmental and epileptic encephalopathy. Molecular investigations of Pro170Arg identify this mutant as a unique representative of the pathogenic variants. Its 100-fold-accelerated GTP uptake is not accompanied by a loss in GTP hydrolysis; Zn2+ ions induce a previously unseen effect on the mutant, forcing it to lose the bound GTP. Our work combining clinical and molecular analyses discovers a novel, biochemically distinct pathogenic missense variant of GNAO1 laying the ground for personalized treatment development.

PAPSS2-related brachyolmia: Clinical and radiological phenotype in 18 new cases.

Brachyolmia is a skeletal dysplasia characterized by short spine-short stature, platyspondyly, and minor long bone abnormalities. We describe 18 patients, from different ethnic backgrounds and ages ranging from infancy to 19 years, with the autosomal recessive form, associated with PAPSS2. The main clinical features include disproportionate short stature with short spine associated with variable symptoms of pain, stiffness, and spinal deformity. Eight patients presented prenatally with short femora, whereas later in childhood their short-spine phenotype emerged. We observed the same pattern of changing skeletal proportion in other patients. The radiological findings included platyspondyly, irregular end plates of the elongated vertebral bodies, narrow disc spaces and short over-faced pedicles. In the limbs, there was mild shortening of femoral necks and tibiae in some patients, whereas others had minor epiphyseal or metaphyseal changes. In all patients, exome and Sanger sequencing identified homozygous or compound heterozygous PAPSS2 variants, including c.809G>A, common to white European patients. Bi-parental inheritance was established where possible. Low serum DHEAS, but not overt androgen excess was identified. Our study indicates that autosomal recessive brachyolmia occurs across continents and may be under-recognized in infancy. This condition should be considered in the differential diagnosis of short femora presenting in the second trimester.

A Novel GDF6 Mutation in a Family with Multiple Synostoses Syndrome without Hearing Loss.

A 4-generation family with multiple synostoses syndrome type 4 (SYNS4) is reported, the third family identified so far. The phenotype segregated with a previously undescribed Asn399Lys (c.1197C>A) substitution in GDF6. N399 is part of a hydrophobic pocket critical for binding the BMP/GDF antagonist noggin. The N399K substitution renders GDF6 more similar to noggin-resistant members of the BMP family, namely GDF2 and BMP10, both of which contain lysine in the corresponding position. To further define the SYNS4 phenotype, we examined 6 of 9 affected family members. The phenotype was carpal and tarsal synostoses with painful feet after walking, but the condition could also be asymptomatic. Interestingly, unlike the previous SYNS4 families, the family presented here has no history of hearing loss, and a 73-year-old mutation carrier had normal audiometry for his age. Based on structure modelling, BMPR2 binding should not be affected by the GDF6-N399K substitution, unlike the S429R and Y444N mutations found in the 2 other families. Hypothetically, this difference may be related to lack of hearing loss.