Primary ovarian insufficiency in a female with phosphomannomutase-2 gene (PMM2) mutations for congenital disorder of glycosylation

Primary ovarian insufficiency: update on clinical and genetic findings

Primary ovarian insufficiency (POI) is a disorder of insufficient ovarian follicle function before the age of 40 years with an estimated prevalence of 3.7% worldwide. Its relevance is emerging due to the increasing number of women desiring conception late or beyond the third decade of their lives. POI clinical presentation is extremely heterogeneous with a possible exordium as primary amenorrhea due to ovarian dysgenesis or with a secondary amenorrhea due to different congenital or acquired abnormalities. POI significantly impacts non only on the fertility prospect of the affected women but also on their general, psychological, sexual quality of life, and, furthermore, on their long-term bone, cardiovascular, and cognitive health. In several cases the underlying cause of POI remains unknown and, thus, these forms are still classified as idiopathic. However, we now know the age of menopause is an inheritable trait and POI has a strong genetic background. This is confirmed by the existence of several candidate genes, experimental and natural models. The most common genetic contributors to POI are the X chromosome-linked defects. Moreover, the variable expressivity of POI defect suggests it can be considered as a multifactorial or oligogenic defect. Here, we present an updated review on clinical findings and on the principal X-linked and autosomal genes involved in syndromic and non-syndromic forms of POI. We also provide current information on the management of the premature hypoestrogenic state as well as on fertility preservation in subjects at risk of POI.

Genetic insights into the complexity of premature ovarian insufficiency

Premature Ovarian Insufficiency (POI) is a highly heterogeneous condition characterized by ovarian dysfunction in women occurring before the age of 40, representing a significant cause of female infertility. It manifests through primary or secondary amenorrhea. While more than half of POI cases are idiopathic, genetic factors play a pivotal role in all instances with known causes, contributing to approximately 20-25% of cases. This article comprehensively reviews the genetic factors associated with POI, delineating the primary candidate genes. The discussion delves into the intricate relationship between these genes and ovarian development, elucidating the functional consequences of diverse mutations to underscore the fundamental impact of genetic effects on POI. The identified genetic factors, encompassing gene mutations and chromosomal abnormalities, are systematically classified based on whether the resulting POI is syndromic or non-syndromic. Furthermore, this paper explores the genetic interplay between mitochondrial genes, such as Required for Meiotic Nuclear Division 1 homolog Gene (RMND1), Mitochondrial Ribosomal Protein S22 Gene (MRPS22), Leucine-rich Pentapeptide Repeat Gene (LRPPRC), and non-coding RNAs, including both microRNAs and Long non-coding RNAs, with POI. The insights provided serve to consolidate and enhance our understanding of the etiology of POI, contributing to establishing a theoretical foundation for diagnosing and treating POI patients, as well as for exploring the mechanisms underlying the disease.

Revisiting the immunopathology of congenital disorders of glycosylation: an updated review

Glycosylation is a critical post-translational modification that plays a pivotal role in several biological processes, such as the immune response. Alterations in glycosylation can modulate the course of various pathologies, such as the case of congenital disorders of glycosylation (CDG), a group of more than 160 rare and complex genetic diseases. Although the link between glycosylation and immune dysfunction has already been recognized, the immune involvement in most CDG remains largely unexplored and poorly understood. In this study, we provide an update on the immune dysfunction and clinical manifestations of the 12 CDG with major immune involvement, organized into 6 categories of inborn errors of immunity according to the International Union of Immunological Societies (IUIS). The immune involvement in phosphomannomutase 2 (PMM2)-CDG - the most frequent CDG - was comprehensively reviewed, highlighting a higher prevalence of immune issues during infancy and childhood and in R141H-bearing genotypes. Finally, using PMM2-CDG as a model, we point to links between abnormal glycosylation patterns in host cells and possibly favored interactions with microorganisms that may explain the higher susceptibility to infection. Further characterizing immunopathology and unusual host-pathogen adhesion in CDG can not only improve immunological standards of care but also pave the way for innovative preventive measures and targeted glycan-based therapies that may improve quality of life for people living with CDG.

Selected Genetic Factors Associated with Primary Ovarian Insufficiency

Primary ovarian insufficiency (POI) is a heterogeneous disease resulting from non-functional ovaries in women before the age of 40. It is characterized by primary amenorrhea or secondary amenorrhea. As regards its etiology, although many POI cases are idiopathic, menopausal age is a heritable trait and genetic factors play an important role in all POI cases with known causes, accounting for approximately 20% to 25% of cases. This paper reviews the selected genetic causes implicated in POI and examines their pathogenic mechanisms to show the crucial role of genetic effects on POI. The genetic factors that can be found in POI cases include chromosomal abnormalities (e.g., X chromosomal aneuploidies, structural X chromosomal abnormalities, X-autosome translocations, and autosomal variations), single gene mutations (e.g., newborn ovary homeobox gene (NOBOX), folliculogenesis specific bHLH transcription factor (FIGLA), follicle-stimulating hormone receptor (FSHR), forkhead box L2 (FOXL2), bone morphogenetic protein 15 (BMP15), etc., as well as defects in mitochondrial functions and non-coding RNAs (small ncRNAs and long ncRNAs). These findings are beneficial for doctors to diagnose idiopathic POI cases and predict the risk of POI in women.

Maternal Uniparental Isodisomy of Chromosome 4 and 8 in Patients with Retinal Dystrophy: SRD5A3-Congenital Disorders of Glycosylation and RP1-Related Retinitis Pigmentosa

Purpose: Uniparental disomy (UPD) is a rare chromosomal abnormality. We performed whole-exosome sequencing (WES) in cases of early-onset retinal dystrophy and identified two cases likely caused by UPD. Herein, we report these two cases and attempt to clarify the clinical picture of retinal dystrophies caused by UPD. Methods: WES analysis was performed for two patients and their parents, who were not consanguineous. Functional analysis was performed in cases suspected of congenital disorders of glycosylation (CDG). We obtained clinical case data and reviewed the literature. Results: In case 1, a novel c.57G>C, p.(Trp19Cys) variant in SRD5A3 was detected homozygously. Genetic analysis suggested a maternal UPD on chromosome 4, and functional analysis confirmed CDG. Clinical findings showed early-onset retinal dystrophy, intellectual disability, and epilepsy. In case 2, an Alu insertion (c.4052_4053ins328, p.[Tyr1352Alafs]) in RP1 was detected homozygously. Maternal UPD on chromosome 8 was suspected. The clinical picture was consistent with RP1-related retinitis pigmentosa. Although the clinical features of retinal dystrophy by UPD may vary, most cases present with childhood onset. Conclusions: There have been limited reports of retinal dystrophy caused by UPD, suggesting that it is rare. Genetic counseling may be encouraged in pediatric cases of retinal dystrophy.

Assessing the effects of PMM2 variants on protein stability

Phosphomannomutase 2 deficiency, PMM2-CDG, is the most frequent disorder of protein N-glycosylation. It is an autosomal recessive disease with a broad clinical and biochemical phenotype. Trying to predict the impact of novel variants is often a challenge due to the high number of variants and the difficulty to establish solid genotype-phenotype correlations. A potential useful strategy is to use computational chemistry calculations as a tool from which relevant information on the structural impact of novel variants may be deduced. Here we present our analyses based on four well-known PMM2 deleterious variants (p.(Leu32Arg), p.(Asp65Tyr), p.(Phe119Leu), p.(Arg141His)) and the polymorphic p.(Glu197Ala) for which we have predicted the effect on protein stability. Our work predicts the effect of different amino acid residues on the conformation and stability of PMM2. These computational simulations are, therefore, an extremely useful methodology which, in combination with routinely used in silico methods of pathogenicity prediction, may help to reveal the structural impact of novel variants at the protein level, potentially leading to a better understanding of target biological molecules.