Next-Generation Sequencing Reveals Novel Genetic Variants (SRY, DMRT1, NR5A1, DHH, DHX37) in Adults With 46,XY DSD

SEC31A may be associated with pituitary hormone deficiency and gonadal dysgenesis

PURPOSE

Disorders/differences of sex development (DSD) result from variants in many different human genes but, frequently, have no detectable molecular cause.

METHODS

Detailed clinical and genetic phenotyping was conducted on a family with three children. A Sec31a animal model and functional studies were used to investigate the significance of the findings.

RESULTS

By trio whole-exome DNA sequencing we detected a heterozygous de novo nonsense SEC31A variant, in three children of healthy non-consanguineous parents. The children had different combinations of disorders that included complete gonadal dysgenesis and multiple pituitary hormone deficiency. SEC31A encodes a component of the COPII coat protein complex, necessary for intracellular anterograde vesicle-mediated transport between the endoplasmic reticulum (ER) and Golgi. CRISPR-Cas9 targeted knockout of the orthologous Sec31a gene region resulted in early embryonic lethality in homozygous mice. mRNA expression of ER-stress genes ATF4 and CHOP was increased in the children, suggesting defective protein transport. The pLI score of the gene, from gnomAD data, is 0.02.

CONCLUSIONS

SEC31A might underlie a previously unrecognised clinical syndrome comprising gonadal dysgenesis, multiple pituitary hormone deficiencies, dysmorphic features and developmental delay. However, a variant that remains undetected, in a different gene, may alternatively be causal in this family.

A conserved NR5A1-responsive enhancer regulates SRY in testis-determination

The Y-linked SRY gene initiates mammalian testis-determination. However, how the expression of SRY is regulated remains elusive. Here, we demonstrate that a conserved steroidogenic factor-1 (SF-1)/NR5A1 binding enhancer is required for appropriate SRY expression to initiate testis-determination in humans. Comparative sequence analysis of SRY 5' regions in mammals identified an evolutionary conserved SF-1/NR5A1-binding motif within a 250 bp region of open chromatin located 5 kilobases upstream of the SRY transcription start site. Genomic analysis of 46,XY individuals with disrupted testis-determination, including a large multigenerational family, identified unique single-base substitutions of highly conserved residues within the SF-1/NR5A1-binding element. In silico modelling and in vitro assays demonstrate the enhancer properties of the NR5A1 motif. Deletion of this hemizygous element by genome-editing, in a novel in vitro cellular model recapitulating human Sertoli cell formation, resulted in a significant reduction in expression of SRY. Therefore, human NR5A1 acts as a regulatory switch between testis and ovary development by upregulating SRY expression, a role that may predate the eutherian radiation. We show that disruption of an enhancer can phenocopy variants in the coding regions of SRY that cause human testis dysgenesis. Since disease causing variants in enhancers are currently rare, the regulation of gene expression in testis-determination offers a paradigm to define enhancer activity in a key developmental process.

Steroidogenic Factor-1 form and function: From phospholipids to physiology

Steroidogenic Factor-1 (SF-1, NR5A1) is a member of the nuclear receptor superfamily of ligand-regulated transcription factors, consisting of a DNA-binding domain (DBD) connected to a transcriptional regulatory ligand binding domain (LBD) via an unstructured hinge domain. SF-1 is a master regulator of development and adult function along the hypothalamic pituitary adrenal and gonadal axes, with strong pathophysiological association with endometriosis and adrenocortical carcinoma. SF-1 was shown to bind and be regulated by phospholipids, one of the most interesting aspects of SF-1 regulation is the manner in which SF-1 interacts with phospholipids: SF-1 buries the phospholipid acyl chains deep in the hydrophobic core of the SF-1 protein, while the lipid headgroups remain solvent-exposed on the exterior of the SF-1 protein surface. Here, we have reviewed several aspects of SF-1 structure, function and physiology, touching on other transcription factors that help regulate SF-1 target genes, non-canonical functions of SF-1, the DNA-binding properties of SF-1, the use of mass spectrometry to identify lipids that associate with SF-1, how protein phosphorylation regulates SF-1 and the structural biology of the phospholipid-ligand binding domain. Together this review summarizes the form and function of Steroidogenic Factor-1 in physiology and in human disease, with particular emphasis on adrenal cancer.

Two Novel Heterozygous Variants in RecA2 Domain of DHX37 Cause 46,XY Gonadal Dysgenesis and Testicular Regression Syndrome

INTRODUCTION

The pathogenic variants in DEAH-box RNA helicase DHX37 are one of the major causes of 46,XY gonadal dysgenesis and testicular regression syndrome (TRS). To date, only 13 different missense variants have been reported. We report two additional cases with different clinical presentations carrying two novel variants in the DHX37 gene.

CASE PRESENTATION AND RESULTS

Case 1 (4.4-year-old boy) presented with significant micropenis and cryptorchidism and was diagnosed as TRS. Case 2 (13.5-year-old girl) had a 46,XY karyotype with female external genitalia and was diagnosed as GD. Two novel DHX37 variants affecting the RecA2 domain, p.G478R and p.L627F, were identified in these cases. Both variants identified in the probands were also present in their unaffected mother.

CONCLUSION

Our findings broaden the variant spectrum of DHX37 in 46,XY differences of sex development (DSD) individuals.

DHX37 and NR5A1 Variants Identified in Patients with 46,XY Partial Gonadal Dysgenesis

The group of disorders known as 46,XY gonadal dysgenesis (GD) is characterized by anomalies in testis determination, including complete and partial GD (PGD) and testicular regression syndrome (TRS). Several genes are known to be involved in sex development pathways, however approximately 50% of all cases remain elusive. Recent studies have identified variants in DHX37, a gene encoding a putative RNA helicase essential in ribosome biogenesis and previously associated with neurodevelopmental disorders, as a cause of PGD and TRS. To investigate the potential role of DHX37 in disorders of sexual development (DSD), 25 individuals with 46,XY DSD were analyzed and putative pathogenic variants were found in four of them. WES analyses were performed on these patients. In DHX37, the variant p.(Arg308Gln), recurrent associated with DSD, was identified in one patient; the p.(Leu467Val), predicted to be deleterious, was found together with an NR5A1 loss-of-function variant in patient 2; and, the p.(Val999Met) was identified in two unrelated patients, one of whom (patient 3) also carried a pathogenic NR5A1 variant. For both patients carrying DHX37 and NR5A1 pathogenic variants, a digenic inheritance is suggested. Our findings support the importance of DHX37 variants as a cause of disorders of sex development, implying a role in testis development.

Nuclear Receptor Gene Variants Underlying Disorders/Differences of Sex Development through Abnormal Testicular Development

Gonadal development is the first step in human reproduction. Aberrant gonadal development during the fetal period is a major cause of disorders/differences of sex development (DSD). To date, pathogenic variants of three nuclear receptor genes (NR5A1, NR0B1, and NR2F2) have been reported to cause DSD via atypical testicular development. In this review article, we describe the clinical significance of the NR5A1 variants as the cause of DSD and introduce novel findings from recent studies. NR5A1 variants are associated with 46,XY DSD and 46,XX testicular/ovotesticular DSD. Notably, both 46,XX DSD and 46,XY DSD caused by the NR5A1 variants show remarkable phenotypic variability, to which digenic/oligogenic inheritances potentially contribute. Additionally, we discuss the roles of NR0B1 and NR2F2 in the etiology of DSD. NR0B1 acts as an anti-testicular gene. Duplications containing NR0B1 result in 46,XY DSD, whereas deletions encompassing NR0B1 can underlie 46,XX testicular/ovotesticular DSD. NR2F2 has recently been reported as a causative gene for 46,XX testicular/ovotesticular DSD and possibly for 46,XY DSD, although the role of NR2F2 in gonadal development is unclear. The knowledge about these three nuclear receptors provides novel insights into the molecular networks involved in the gonadal development in human fetuses.

Phenotype and genetic characteristics in 20 Chinese patients with 46,XY disorders of sex development

PURPOSE

46,XY disorders of sex development (DSD) is the most complicated and common type of DSD. To date, more than 30 genes have been identified associated with 46,XY DSD. However, the mutation spectrum of 46,XY DSD is incomplete owing to the high genetic and clinical heterogeneity. This study aims to provide clinical and mutational characteristics of 18 Chinese patients with 46,XY DSD.

METHODS

A total of 20 unrelated individuals with 46,XY DSD were recruited. Whole-exome sequencing (WES) or custom-panel sequencing combined Sanger sequencing were performed to detect the pathogenic mutations. The pathogenicity of the variant was assessed according to the American College of Medical Genetics and Genomics (ACMG) guidance and technical standards recommended by the ACMG and the Clinical Genome Resource (ClinGen).

RESULTS

Six patients harbored NR5A1 mutations; two patients harbored NR0B1 mutations; six patients harbored SRD5A2 mutations; six patients harbored AR mutations. Six novel genetic variants were identified involved in three genes (NR5A1, NR0B1, and AR).

CONCLUSION

We determined the genetic etiology for all enrolled patients. Our study expanded the mutation spectrum of 46,XY DSD and provided diagnostic evidence for patients with the same mutation in the future.

Functional assessment of DMRT1 variants and their pathogenicity for isolated male infertility

OBJECTIVE

To study the impact of Doublesex and mab-3-related transcription factor 1 (DMRT1) gene variants on the encoded protein's function and the variants' pathogenic relevance for isolated male infertility caused by azoospermia.

DESIGN

This study established a novel luciferase assay for DMRT1 missense variants using 2 different target promotors and validated the assay by analyzing previously published variants associated with differences in sex development.

SETTING

University genetics research institute and tertiary referral center for couples' infertility.

PATIENT(S)

Eleven infertile men with severely impaired spermatogenesis resulting in crypto- or azoospermia and carrying rare heterozygous missense variants in DMRT1 were identified within the Male Reproductive Genomics study.

MAIN OUTCOME MEASURE(S)

Luciferase assays with human DMRT1 variants to test functional effects on the CYP19A1 and Stra8 target promoters.

RESULT(S)

We first developed and refined luciferase assays to reliably test the functional impact of DMRT1 missense variants. Next, the assay was validated by analyzing 2 DMRT1 variants associated with differences in sex development, of which c.240G>C p.(Arg80Ser) displayed highly significant effects on both target promoters compared with the wild-type protein (-40% and +100%, respectively) and c.331A>G p.(Arg111Gly) had a significant effect on the Stra8 promoter (-76%). We then systematically characterized 11 DMRT1 variants identified in infertile men. The de novo variant c.344T>A p.(Met115Lys) showed a pronounced loss of function in both DMRT1 target promoters (-100% and -86%, respectively). Variants c.308A>G p.(Lys103Arg) and c.991G>C p.(Asp331His) showed a significant gain of function exclusively for the CYP19A1 promoter (+15% and +19%, respectively). Based on these results, 3 variants were reclassified according to clinical guidelines.

CONCLUSION(S)

The present study highlights the importance of functionally characterizing DMRT1 variants of uncertain clinical significance. Using luciferase assays for diagnostic purposes enables an improved causal diagnosis for isolated male infertility.

Comprehensive molecular analysis identifies eight novel variants in XY females with disorders of sex development

Disorders of sex development (DSD) are a group of clinical conditions with variable presentation and genetic background. Females with or without development of secondary sexual characters and presenting with primary amenorrhea (PA) and a 46,XY karyotype are one of the classified groups in DSD. In this study, we aimed to determine the genetic mutations in 25 females with PA and a 46,XY karyotype to show correlations with their phenotypes. Routine Sanger sequencing with candidate genes like SRY, AR, SRD5A2, and SF1, which are mainly responsible for 46,XY DSD in adolescent females, was performed. In a cohort of 25 patients of PA with 46,XY DSD, where routine Sanger sequencing failed to detect the mutations, next-generation sequencing of a targeted gene panel with 81 genes was used for the molecular diagnosis. The targeted sequencing identified a total of 21 mutations including 8 novel variants in 20 out of 25 patients with DSD. The most frequently identified mutations in our series were in AR (36%), followed by SRD5A2 (20%), SF1 (12%), DHX37 (4%), HSD17B3 (4%), and DMRT2 (4%). We could not find any mutation in the DSD-related genes in five (20%) patients due to complex molecular mechanisms in 46,XY DSD, highlighting the possibility of new DSD genes which are yet to be discovered in these disorders. In conclusion, genetic testing, including cytogenetics and molecular genetics, is important for the diagnosis and management of 46,XY DSD cases.

A novel DEAH-box helicase 37 mutation associated with differences of sex development

OBJECTIVE

To determine the genetic etiology of a family pedigree with two patients affected by differences of sex development (DSD).

METHODS

Assess the clinical characteristics of the patients and achieve exome sequencing results and in vitro functional studies.

RESULTS

The 15-year-old proband, raised as female, presented with delayed puberty and short stature associated with atypical genitalia. Hormonal profile showed hypergonadotrophic hypogonadism. Imaging studies revealed the absence of a uterus and ovaries. The karyotype confirmed a 46, XY pattern. Her younger brother presented with a micropenis and hypoplastic scrotum with non-palpable testis and hypospadias. Laparoscopic exploration was performed on the younger brother. Streak gonads were found and removed due to the risk of neoplastic transformation. Post-operative histopathology showed the co-existence of Wolffian and Müllerian derivatives. Whole-exome sequencing identified a novel mutation (c.1223C>T, p. Ser408Leu) in the Asp-Glu-Ala-His-box helicase 37 gene, which was found to be deleterious by in silico analysis. Segregation analysis of the variant displayed a sex-limited, autosomal dominant, maternal inheritance pattern. In vitro experiments revealed that the substitution of 408Ser by Leu caused decreased DHX37 expression both at the mRNA and protein levels. Moreover, the β-catenin protein was upregulated, and the p53 protein was unaltered by mutant DHX37.

CONCLUSIONS

We described a novel mutation (c.1223C>T, p. Ser408Leu) of the DHX37 gene associated with a Chinese pedigree consisting of two 46, XY DSD patients. We speculated that the underlying molecular mechanism might involve upregulation of the β-catenin protein.

Genomics of sexual cell fate transdifferentiation in the mouse gonad

Sex determination in mammals hinges on a cell fate decision in the fetal bipotential gonad between formation of male Sertoli cells or female granulosa cells. While this decision normally is permanent, loss of key cell fate regulators such as the transcription factors Dmrt1 and Foxl2 can cause postnatal transdifferentiation from Sertoli to granulosa-like (Dmrt1) or vice versa (Foxl2). Here, we examine the mechanism of male-to-female transdifferentiation in mice carrying either a null mutation of Dmrt1 or a point mutation, R111G, that alters the DNA-binding motif and causes human XY gonadal dysgenesis and sex reversal. We first define genes misexpressed during transdifferentiation and then show that female transcriptional regulators driving transdifferentiation in the mutant XY gonad (ESR2, LRH1, FOXL2) bind chromatin sites related to those normally bound in the XX ovary. We next define gene expression changes and abnormal chromatin compartments at the onset of transdifferentiation that may help destabilize cell fate and initiate the transdifferentiation process. We model the R111G mutation in mice and show that it causes dominant gonadal dysgenesis, analogous to its human phenotype but less severe. We show that R111G partially feminizes the testicular transcriptome and causes dominant disruption of DMRT1 binding specificity in vivo. These data help illuminate how transdifferentiation occurs when sexual cell fate maintenance is disrupted and identify chromatin sites and transcripts that may play key roles in the transdifferentiation process.

A Single-Center, Observational Study of 607 Children and Young People Presenting With Differences of Sex Development (DSD)

Context

Differences of sex development (DSD) represent a wide range of conditions presenting at different ages to various health professionals. Establishing a diagnosis, supporting the family, and developing a management plan are important.

Objective

We aimed to better understand the presentation and prevalence of pediatric DSD.

Methods

A retrospective, observational cohort study was undertaken in a single tertiary pediatric center of all children and young people (CYP) referred to a DSD multidisciplinary team over 25 years (1995-2019). In total, 607 CYP (520 regional referrals) were included. Data were analyzed for diagnosis, sex-assignment, age and mode of presentation, additional phenotypic features, mortality, and approximate point prevalence.

Results

Among the 3 major DSD categories, sex chromosome DSD was diagnosed in 11.2% (68/607) (most commonly 45,X/46,XY mosaicism), 46,XY DSD in 61.1% (371/607) (multiple diagnoses often with associated features), while 46,XX DSD occurred in 27.7% (168/607) (often 21-hydroxylase deficiency). Most children (80.1%) presented as neonates, usually with atypical genitalia, adrenal insufficiency, undescended testes or hernias. Those presenting later had diverse features. Rarely, the diagnosis was made antenatally (3.8%, n = 23) or following incidental karyotyping/family history (n = 14). Mortality was surprisingly high in 46,XY children, usually due to complex associated features (46,XY girls, 8.3%; 46,XY boys, 2.7%). The approximate point prevalence of neonatal referrals for investigation of DSD was 1 in 6347 births, and 1 in 5101 overall throughout childhood.

Conclusion

DSD represent a diverse range of conditions that can present at different ages. Pathways for expert diagnosis and management are important to optimize care.

Management of a Girl With Delayed Puberty and Elevated Gonadotropins

A girl presenting with delayed puberty and elevated gonadotropins may have a range of conditions such as Turner syndrome (TS), primary ovarian insufficiency (POI), and 46,XY disorders of sexual development (DSD). An organized and measured approach to investigation can help reach a timely diagnosis. Management of young people often requires specialist multidisciplinary input to address the endocrine and nonendocrine features of these complex conditions, as well as the psychological challenges posed by their diagnosis. Next-generation sequencing within the research setting has revealed several genetic causes of POI and 46,XY DSD, which may further facilitate an individualized approach to care of these young people in the future. Pubertal induction is required in many and the timing of this may need to be balanced with other issues specific to the condition (eg, allowing time for information-sharing in 46,XY DSD, optimizing growth in TS). Shared decision-making and sign-posting to relevant support groups from the outset can help empower young people and their families to manage these conditions. We describe 3 clinical vignettes of girls presenting with delayed puberty and hypergonadotropic amenorrhea and discuss their clinical management in the context of current literature and guidelines.

Novel Genomic Variants, Atypical Phenotypes and Evidence of a Digenic/Oligogenic Contribution to Disorders/Differences of Sex Development in a Large North African Cohort

In a majority of individuals with disorders/differences of sex development (DSD) a genetic etiology is often elusive. However, new genes causing DSD are routinely reported and using the unbiased genomic approaches, such as whole exome sequencing (WES) should result in an increased diagnostic yield. Here, we performed WES on a large cohort of 125 individuals all of Algerian origin, who presented with a wide range of DSD phenotypes. The study excluded individuals with congenital adrenal hypoplasia (CAH) or chromosomal DSD. Parental consanguinity was reported in 36% of individuals. The genetic etiology was established in 49.6% (62/125) individuals of the total cohort, which includes 42.2% (35/83) of 46, XY non-syndromic DSD and 69.2% (27/39) of 46, XY syndromic DSD. No pathogenic variants were identified in the 46, XX DSD cases (0/3). Variants in the AR, HSD17B3, NR5A1 and SRD5A2 genes were the most common causes of DSD. Other variants were identified in genes associated with congenital hypogonadotropic hypogonadism (CHH), including the CHD7 and PROKR2. Previously unreported pathogenic/likely pathogenic variants (n = 30) involving 25 different genes were identified in 22.4% of the cohort. Remarkably 11.5% of the 46, XY DSD group carried variants classified as pathogenic/likely pathogenic variant in more than one gene known to cause DSD. The data indicates that variants in PLXNA3, a candidate CHH gene, is unlikely to be involved in CHH. The data also suggest that NR2F2 variants may cause 46, XY DSD.

Case Report: Long-term follow-up of desert hedgehog variant caused 46, XY gonadal dysgenesis with multiple complications in a Chinese child

Background: Desert hedgehog (DHH), as a member of the Hedgehog (HH) family, is mainly involved in testicular development and peripheral nerve sheath formation. A DHH variant has been identified in patients with 46, XY gonadal dysgenesis (46, XY GD) with or without neuropathy, but few reports mention the involvement of other complications.

Case presentation: Here, we report a Chinese female patient who was hospitalized at 14.3 years old due to slow breast development for more than 1 year. She had a female genitalia phenotype and breast development started at 13 years old but progressed slowly. She was not yet menarche on admission, and she had intermittent muscle cramps in her hands and feet. Her karyotype analysis was 46, XY and the SRY gene was positive. Surgical exploration revealed no uterus or ovaries, and the pathology of bilateral gonads was dysplastic testis tissue, which was consistent with partial gonadal dysgenesis (PGD). Genetic analysis identified a homozygous pathogenic variant in DHH exon 3 (c.1027T>C, p. Cys343Arg). During the 6-year follow-up, she received estrogen replacement therapy, resulting in breast development progression without gender dysphoria. However, her peripheral neuropathy became more obvious, and a nerve conduction study (NCS) indicated decreased nerve conduction velocity and action potential. In addition, she also suffered complications such as obesity, insulin resistance, fatty liver, and gastric ulcers.

Conclusion: In the present study, we reported a case of 46, XY GD with minifascicular neuropathy caused by a DHH homozygous variant, and we summarized the reported cases worldwide. For the first time in such patients, we showed a comparison of NCS changes with age as well as the presence of multiple complications not previously reported.

Whole exome sequencing applied to 42 Han Chinese patients with posterior hypospadias

Hypospadias, a malformation of male external genitalia, is characterized by an aberrant opening of the urethra on the ventral side of the penis. It is considered a complex disorder with both environmental and genetic factors involved in its pathogenesis. To identify the genetic abnormality involved in the pathogenesis of hypospadias, we performed whole exome sequencing (WES) analysis in 42 hypospadias patients with karyotype 46, XY in the Nanhai Meternity&Child Health Hospital of Foshan. All the likely pathogenic variants were confirmed by Sanger sequencing and assessed by Sorting Intolerant from Tolerant (SIFT), PROVEAN, PolyPhen2, ClinPred, LRT, Mutation Assessor, FATHMM, and GERP software. We discovered 27 gene mutations in 20 patients, including eight cases of the SRD5A2 gene, 4 cases of the AR gene, 3 cases of the CYP17A1 gene, 1 case of the WT1 gene, 1 case of the ANOS1 gene, 1 case of the NR5A1 gene, 1 case of the FGFR1 gene, and one case of the DHX37 gene. Our study is the first to describe six novel missense mutations, AR(c.302G > A, c.2593G > T, and c.1705G > T), CYP17A1(c.1298 T > C), FGFR1 (c.995C > T) and DHX37(c.923G > A). In summary, genetic defect detection was useful for early diagnosis of severe hypospadias in the Han Chinese population. Nevertheless, most cases remain unexplained, and the exact pathogenesis of hypospadias still needs further study.

DHX37 and 46,XY DSD: A New Ribosomopathy?

Recently, a series of recurrent missense variants in the RNA-helicase DHX37 have been reported associated with either 46,XY gonadal dysgenesis, 46,XY testicular regression syndrome (TRS), or anorchia. All affected children have non-syndromic forms of disorders/differences of sex development (DSD). These variants, which involve highly conserved amino acids within known functional domains of the protein, are predicted by in silico tools to have a deleterious effect on helicase function. DHX37 is required for ribosome biogenesis in eukaryotes, and how these variants cause DSD is unclear. The relationship between DHX37 and human congenital disorders is complex as compound heterozygous as well as de novo heterozygous missense variants in DHX37 are also associated with a complex congenital developmental syndrome (NEDBAVC, neurodevelopmental disorder with brain anomalies and with or without vertebral or cardiac anomalies; OMIM 618731), consisting of microcephaly, global developmental delay, seizures, facial dysmorphia, and kidney and cardiac anomalies. Here, we will give a brief overview of ribosome biogenesis and the role of DHX37 in this process. We will discuss variants in DHX37, their contribution to human disease in the general context of human ribosomopathies, and the possible disease mechanisms that may be involved.

Temporal sociomedical approaches to intersex* bodies

The history of the field of intersex bodies/bodies with variations of sex development (VSD) reflects the ongoing tension between sociomedical attempts to control uncertainty and reduce the duration of corporeal uncertainty by means of early diagnosis and treatment, and the embodied subjects who resist or challenge these attempts, which ultimately increase uncertainty. Based on various qualitative studies in the field of intersex, this article describes three temporal sociomedical approaches that have evolved over the last decade and aims to address the uncertainty surrounding intersex/VSD bodies. These approaches are (1) the corrective-concealing approach, which includes early surgeries and hormone therapies intended to "correct" intersex conditions and the deliberate concealment of the ambiguity and uncertainty associated with intersex conditions; (2) the preventive approach, which involves early genetic diagnostic methods aimed at regulating or preventing the recurrence of hereditary conditions under the umbrella of VSD; and (3) the wait-and-see approach, which perceives intersex bodies as natural variations and encourages parents to take time, wait, and give their children the right to bodily autonomy. A comparison of these approaches from biopolitical, phenomenological, and pragmatic perspectives reveals that time is an essential social agent in addressing and controlling uncertainty, a gatekeeper of social norms and social and physical orders, and, on the other hand, a sociopolitical agent that enables creative social change.

Genomic variants reducing expression of two endocytic receptors in 46,XY differences of sex development

Transporter-dependent steroid hormone uptake into target cells was demonstrated in genetically engineered mice and fruit flies. We hypothesized that mutations in such transporters may cause differences in sex development (DSD) in humans. Exome sequencing was performed in 16 genetically unsolved cases of 46,XY DSD selected from an anonymized collection of 708 lines of genital fibroblasts (GF) that were taken from individuals with incomplete virilization. Selection criteria were based on available biochemical characterization of GF compatible with reduced androgen uptake. Two unrelated individuals were identified with mutations in LDL receptor-related protein 2 (LRP2), a gene previously associated with partial sex steroid insensitivity in mice. Like Lrp2^-/- mice, affected individuals had non-descended testes. Western blots on GF confirmed reduced LRP2 expression, and endocytosis of sex hormone-binding globulin was reduced. In three unrelated individuals, two with undescended testes, mutations in another endocytic receptor gene, limb development membrane protein 1 like (LMBR1L), were detected. Two of these individuals had mutations affecting the same codon. In a transfected cell model, mutated LMBR1L showed reduced cell surface expression. Our findings suggest that endocytic androgen uptake in complex with sex hormone-binding globulin is relevant in human. LMBR1L may play a similar role in androgen uptake.

OUP accepted manuscript

The pathways of gametogenesis encompass elaborate cellular specialization accompanied by precise partitioning of the genome content in order to produce fully matured spermatozoa and oocytes. Transcription factors are an important class of molecules that function in gametogenesis to regulate intrinsic gene expression programs, play essential roles in specifying (or determining) germ cell fate and assist in guiding full maturation of germ cells and maintenance of their populations. Moreover, in order to reinforce or redirect cell fate in vitro, it is transcription factors that are most frequently induced, over-expressed or activated. Many reviews have focused on the molecular development and genetics of gametogenesis, in vivo and in vitro, in model organisms and in humans, including several recent comprehensive reviews: here, we focus specifically on the role of transcription factors. Recent advances in stem cell biology and multi-omic studies have enabled deeper investigation into the unique transcriptional mechanisms of human reproductive development. Moreover, as methods continually improve, in vitro differentiation of germ cells can provide the platform for robust gain- and loss-of-function genetic analyses. These analyses are delineating unique and shared human germ cell transcriptional network components that, together with somatic lineage specifiers and pluripotency transcription factors, function in transitions from pluripotent stem cells to gametes. This grand theme review offers additional insight into human infertility and reproductive disorders that are linked predominantly to defects in the transcription factor networks and thus may potentially contribute to the development of novel treatments for infertility.

A conserved function of Human DLC3 and Drosophila Cv-c in testis development

The identification of genes affecting gonad development is essential to understand the mechanisms causing Variations/Differences in Sex Development (DSD). Recently, a DLC3 mutation was associated with male gonadal dysgenesis in 46,XY DSD patients. We have studied the requirement of Cv-c, the Drosophila ortholog of DLC3, in Drosophila gonad development, as well as the functional capacity of DLC3 human variants to rescue cv-c gonad defects. We show that Cv-c is required to maintain testis integrity during fly development. We find that Cv-c and human DLC3 can perform the same function in fly embryos, as flies carrying wild type but not patient DLC3 variations can rescue gonadal dysgenesis, suggesting functional conservation. We also demonstrate that the StART domain mediates Cv-c's function in the male gonad independently from the GAP domain's activity. This work demonstrates a role for DLC3/Cv-c in male gonadogenesis and highlights a novel StART domain mediated function required to organize the gonadal mesoderm and maintain its interaction with the germ cells during testis development.

DMRT1: An Ancient Sexual Regulator Required for Human Gonadogenesis

Transcriptional regulators related to the invertebrate sexual regulators doublesex and mab-3 occur throughout metazoans and control sex in most animal groups. Seven of these DMRT genes are found in mammals, and mouse genetics has shown that one, Dmrt1, plays a crucial role in testis differentiation, both in germ cells and somatic cells. Deletions and, more recently, point mutations affecting human DMRT1 have demonstrated that its heterozygosity is associated with 46,XY complete gonadal dysgenesis. Most of our detailed knowledge of DMRT1 function in the testis, the focus of this review, derives from mouse studies, which have revealed that DMRT1 is essential for male somatic and germ cell differentiation and maintenance of male somatic cell fate after differentiation. Moreover, ectopic DMRT1 can reprogram differentiated female granulosa cells into male Sertoli-like cells. The ability of DMRT1 to control sexual cell fate likely derives from at least 3 properties. First, DMRT1 functionally collaborates with another key male sex regulator, SOX9, and possibly other proteins to maintain and reprogram sexual cell fate. Second, and related, DMRT1 appears to function as a pioneer transcription factor, binding "closed" inaccessible chromatin and promoting its opening to allow binding by other regulators including SOX9. Third, DMRT1 binds DNA by a highly unusual form of interaction and can bind with different stoichiometries.

Genetics of 46,XY gonadal dysgenesis

In 46,XY men, testis is determined by a genetic network(s) that both promotes testis formation and represses ovarian development. Disruption of this process results in a lack of testis-determination and affected individuals present with 46,XY gonadal dysgenesis (GD), a part of the spectrum of Disorders/Differences of Sex Development/Determination (DSD). A minority of all cases of GD are associated with pathogenic variants in key players of testis-determination, SRY, SOX9, MAP3K1 and NR5A1. However, most of the cases remain unexplained. Recently, unbiased exome sequencing approaches have revealed new genes and loci that may cause 46,XY GD. We critically evaluate the evidence to support causality of these factors and describe how functional studies are continuing to improve our understanding of genotype-phenotype relationships in genes that are established causes of GD. As genomic data continues to be generated from DSD cohorts, we propose several recommendations to help interpret the data and establish causality.

Society for Endocrinology UK Guidance on the initial evaluation of a suspected difference or disorder of sex development (Revised 2021)

It is paramount that any child or adolescent with a suspected difference or disorder of sex development (DSD) is assessed by an experienced clinician with adequate knowledge about the range of conditions associated with DSD and is discussed with the regional DSD service. In most cases, the paediatric endocrinologist within this service acts as the first point of contact but involvement of the regional multidisciplinary service will also ensure prompt access to specialist psychology and nursing care. The underlying pathophysiology of DSD and the process of delineating this should be discussed with the parents and affected young person with all diagnostic tests undertaken in a timely fashion. Finally, for rare conditions such as these, it is imperative that clinical experience is shared through national and international clinical and research collaborations.

Molecular and Cytogenetic Analysis of Romanian Patients with Differences in Sex Development

Differences in sex development (DSD) are often correlated with a genetic etiology. This study aimed to assess the etiology of DSD patients following a protocol of genetic testing. Materials and methods. This study prospectively investigated a total of 267 patients with DSD who presented to Clinical Emergency Hospital for Children Cluj-Napoca between January 2012 and December 2019. Each patient was clinically, biochemically, and morphologically evaluated. As a first intervention, the genetic test included karyotype + SRY testing. A high value of 17-hydroxyprogesterone was found in 39 patients, in whom strip assay analysis of the CYP21A2 gene was subsequently performed. A total of 35 patients were evaluated by chromosomal microarray technique, and 22 patients were evaluated by the NGS of a gene panel. Results. The karyotype analysis established the diagnosis in 15% of the patients, most of whom presented with sex chromosome abnormalities. Genetic testing of CYP21A2 established a confirmation of the diagnosis in 44% of patients tested. SNP array analysis was particularly useful in patients with syndromic DSD; 20% of patients tested presented with pathogenic CNVs or uniparental disomy. Gene panel sequencing established the diagnosis in 11 of the 22 tested patients (50%), and the androgen receptor gene was most often involved in these patients. The genes that presented as pathogenic or likely pathogenic variants or variants of uncertain significance were RSPO1, FGFR1, WT1, CHD7, AR, NIPBL, AMHR2, AR, EMX2, CYP17A1, NR0B1, GNRHR, GATA4, and ATM genes. Conclusion. An evaluation following a genetic testing protocol that included karyotype and SRY gene testing, CYP21A2 analysis, chromosomal analysis by microarray, and high-throughput sequencing were useful in establishing the diagnosis, with a spectrum of diagnostic yield depending on the technique (between 15 and 50%). Additionally, new genetic variants not previously described in DSD were observed.

The Desert Hedgehog Signalling Pathway in Human Gonadal Development and Differences of Sex Development

While the Hedgehog signalling pathway is implicated in numerous developmental processes and maladies, variants in the Desert Hedgehog (DHH) ligand underlie a condition characterised by 46,XY gonadal dysgenesis with or without peripheral neuropathy. We discuss here the role and regulation of DHH and its signalling pathway in the developing gonads and examine the current understanding of how disruption to this pathway causes this difference of sex development (DSD) in humans.

Targeted next-generation sequencing panel screening of 668 Chinese patients with non-obstructive azoospermia

PURPOSE

We aimed (1) to determine the molecular diagnosis rate and the recurrent causative genes of patients with non-obstructive azoospermia (NOA) using targeted next-generation sequencing (NGS) panel screening and (2) to discuss whether these genes help in the prognosis for microsurgical testicular sperm extraction (micro-TESE).

METHODS

We used NGS panels to screen 668 Chinese men with NOA. Micro-TESE outcomes for six patients with pathogenic mutations were followed up. Functional assays were performed for two NR5A1 variants identified: p.I224V and p.R281C.

RESULTS

Targeted NGS panel sequencing could explain 4/189 (2.1% by panel 1) or 10/479 (2.1% by panel 2) of the patients with NOA after exclusion of karyotype abnormalities and Y chromosome microdeletions. Almost all mutations detected were newly described except for NR5A1 p.R281C and TEX11 p.M156V. Two missense NR5A1 mutations-p.R281C and p.I244V-were proved to be deleterious by in vitro functional assays. Mutations in TEX11, TEX14, and NR5A1 genes are recurrent causes of NOA, but each gene explains only a very small percentage (less than 4/668; 0.6%). Only the patient with NR5A1 mutations produced viable spermatozoa through micro-TESE, but other patients with TEX11 and TEX14 had poor micro-TESE prognoses.

CONCLUSIONS

A targeted NGS panel is a feasible diagnostic method for patients with NOA. Because each gene implicated explains only a small proportion of such cases, more genes should be included to further increase the diagnostic rate. Considering previous reports, we suggest that only a few genes that are directly linked to meiosis can indicate poor micro-TESE prognosis, such as TEX11, TEX14, and SYCE1.

Expanding DSD Phenotypes Associated with Variants in the DEAH-Box RNA Helicase DHX37

Missense variants in the RNA-helicase DHX37 are associated with either 46,XY gonadal dysgenesis or 46,XY testicular regression syndrome (TRS). DHX37 is required for ribosome biogenesis, and this subgroup of XY DSD is a new human ribosomopathy. In a cohort of 140 individuals with 46,XY DSD, we identified 7 children with either 46,XY complete gonadal dysgenesis or 46,XY TRS carrying rare or novel DHX37 variants. A novel p.R390H variant within the RecA1 domain was identified in a girl with complete gonadal dysgenesis. A paternally inherited p.R487H variant, previously associated with a recessive congenital developmental syndrome, was carried by a boy with a syndromic form of 46,XY DSD. His phenotype may be explained in part by a novel homozygous loss-of-function variant in the NGLY1 gene, which causes a congenital disorder of deglycosylation. Remarkably, a homozygous p.T477H variant was identified in a boy with TRS. His fertile father had unilateral testicular regression with typical male genital development. This expands the DSD phenotypes associated with DHX37. Structural analysis of all variants predicted deleterious effects on helicase function. Similar to all other known ribosomopathies, the mechanism of pathogenesis is unknown.

How Far Should We Explore Hypospadias? Next-generation Sequencing Applied to a Large Cohort of Hypospadiac Patients

BACKGROUND

Next-generation sequencing (NGS) is generally used for patients with severe disorders of sex development (DSD). However, NGS has not been applied extensively for patients with hypospadias only, and most affected children do not benefit from an etiological diagnosis.

OBJECTIVE

To evaluate the clinical usefulness of NGS for patients with hypospadias, regardless of severity.

DESIGN, SETTING, AND PARTICIPANTS

Prospective multicenter research included 293 children with glandular to penoscrotal hypospadias (no undescended testis and no micropenis). After excluding likely pathogenic androgen receptor (AR) variants by Sanger sequencing, an NGS panel tested 336 genes including unexplored candidates in 284 patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The rate of pathogenic and likely pathogenic variants was assessed using REVEL, ClinVar, and in-house tools (Captain-ACHAB, MobiCNV, and MobiDetails).

RESULTS AND LIMITATIONS

Likely pathogenic variants were identified in 16 (5.5%) patients with both Sanger sequencing and NGS taken into account. Some genes were related to DSD (AR, NR5A1, HSD17B3, and MAMLD1), but reverse phenotyping revealed two syndromic disorders with midline defects (MID1) and alteration in the retinoic acid signaling pathway (RARA). Coverage analysis revealed an 18q deletion. Identification of likely pathogenic variants increased with hypospadias severity. Other variants of unknown significance (VUSs) in genes implicated in hypogonadotropic hypogonadism, Noonan syndrome, and genital tubercle development were also identified. Genetic study mainly focused on exonic variants, and most cases remain unexplained.

CONCLUSIONS

NGS reveals minor forms of DSD, undiagnosed syndromes, or candidate rare variants in new genes, indicating that even patients with mild hypospadias benefit from advanced sequencing techniques. Early molecular diagnosis would help improve follow-up at puberty and medical counseling for initially undiagnosed syndromes. Future studies will improve the diagnosis by investigating the contribution of VUSs.

PATIENT SUMMARY

Next-generation sequencing enables simultaneous testing of numerous genes and should not be limited to disorders of sex development cases. Even patients with mild hypospadias would benefit from early diagnosis of a genetic defect implicated in sex development or other syndromes.

Integrative Expression and Prognosis Analysis of DHX37 in Human Cancers by Data Mining

DHEA-Box Helicase 37 (DHX37) is a putative RNA helicase. It is involved in various RNA secondary structure alteration processes, including translation, nuclear splicing, and ribosome assembly. It is reported to be associated with the neurodevelopmental disorder with brain anomalies, and a recent study suggests that DHX37 is a functional regulator of CD8 T cells. Dysregulation of the CD8 T cell function is closely related to defective antitumor immune responses. In the present study, we investigated the expression, mutation, and prognostic role of DHX37 in human cancers, mainly by mining publicly available datasets. Our results suggested that DHX37 was significantly upregulated in 17 kinds of tumors. Mutations including deletions, insertions, and substitutions of DHX37 were widely detected. Besides, the expression of DHX37 was negatively correlated with immune-related genes PD-L1, RGS16, and TOX, and it was positively associated with TIM3, LAG3, and NCOR2. Through biofunctional analysis, we observed that DHX37 was significantly enriched in cancer-related pathways such as cell cycle, DNA replication, mismatch repair, RNA degradation, and RNA polymerase. In conclusion, the study explored the significance of DHX37 in human cancers. DHX37 may serve as a potential target for cancer immunotherapy.

Disorders of sexual development with XY karyotype and female phenotype: clinical findings and genetic background in a cohort from a single centre

PURPOSE

46, XY disorders (or differences) of sex development (DSD) are a group of clinical conditions with variable genetic background; correct diagnosis is often difficult, but it permits to optimize the management. The aim of this study is to identify clinical and genetics features of a group of women with 46, XY DSD to define some issues characterizing people with 46, XY DSD in Italy.

METHODS

Retrospective analysis of girls and women with 46, XY DSD and female phenotype evaluated between year 2000 and 2016, performed by anonymised database, focusing on the clinical features and management, including presentation, first diagnostic suspect, gonadal surgery and molecular diagnostic delay.

RESULTS

A total of 84 records were collected (mean age at clinical presentation: 9.1 ± 7.9 years; mean age at definitive diagnosis: 20.1 ± 15.0 years). Complete androgen insensitivity syndrome was the most common diagnosis (60%). Only 12 patients (14.3%) did not receive a molecular diagnosis. Early misdiagnoses frequently occurred; diagnostic delay was 10.2 ± 11.2 years, being reduced in patients presenting from 2007 to 2016. The discordance between genotypic and phenotypic sex during pregnancy or at birth determined early reason for referral in a considerable percentage (4.9%).

CONCLUSION

Misdiagnosis and long diagnostic delays are present in females with 46, XY DSD in Italy, but the new genetic techniques permit faster right diagnoses in the last years. The centralization in dedicated third level units permits to reduce the number of patients without a molecular diagnosis, allowing better clinical management and appropriate genetic counselling.

46,XY DSD and limb abnormalities in a female with a de novo LHX9 missense mutation

Differences in sex development (DSD) are a group of rare conditions involving genes, hormones and reproductive organs, including genitals. Although these disorders are common, information about the molecular causes remain limited. Many genes have been identified in association with DSD but in many cases the causative gene could not be identified. The Lhx9 gene has been studied in mice and birds, and biallelic mutations in this gene have been found to cause 46,XY DSD and limb abnormalities. So far two variants of LHX9 have been identified in 46,XY individuals with testicular regression, micropenis and hypospadias. We report a de novo heterozygous missense variant in LHX9 in a girl with 46,XY DSD and finger and toe abnormalities. It was previously predicted that a mutation in LHX9 would not cause extragenital anomalies in light of prior animal studies, but our report adds to the limited knowledge of the phenotype observed in humans with a variant in LHX9. To the best of our knowledge this is the first reported case with this combination of abnormalities.

FGF9 is a downstream target of SRY and sufficient to determine male sex fate in ex vivo XX gonad culture

Fibroblast growth factor 9 (FGF9) is an autocrine/paracrine growth factor that plays critical roles in embryonic and organ developments and is involved in diverse physiological events. Loss of function of FGF9 exhibits male-to-female sex reversal in the transgenic mouse model and gain of FGF9 copy number was found in human 46, XX sex reversal patient with disorders of sex development. These results suggested that FGF9 plays a vital role in male sex development. Nevertheless, how FGF9/Fgf9 expression is regulated during testis determination remains unclear. In this study, we demonstrated that human and mouse SRY bind to -833 to -821 of human FGF9 and -1010 to -998 of mouse Fgf9, respectively, and control FGF9/Fgf9 mRNA expression. Interestingly, we showed that mouse SRY cooperates with SF1 to regulate Fgf9 expression, whereas human SRY-mediated FGF9 expression is SF1 independent. Furthermore, using an ex vivo gonadal culture system, we showed that FGF9 expression is sufficient to switch cell fate from female to male sex development in 12-16 tail somite XX mouse gonads. Taken together, our findings provide evidence to support the SRY-dependent, fate-determining role of FGF9 in male sex development.

Identification of a possible association of JAK2 in development of microphthalmia, anophthalmia, and coloboma (MAC) complex in a child with 9p deletion and duplication

BACKGROUND

Microphthalmia, anophthalmia, coloboma (MAC) complex is a spectrum of ocular abnormalities that occur in isolation or as part of a syndrome. Genetic abnormalities have been shown to account for 80% of cases in bilateral anophthalmia or severe microphthalmia, where 25-30% were attributed to chromosomal defects in this subset of MAC patients. To date, chromosome 9 short arm (9p) abnormalities have not been shown to associate with development of MAC.

PURPOSE

To report a case of MAC spectrum disorder that is related to 9p deletion and duplication.

MATERIALS AND METHODS

A child who exhibited signs of MAC was evaluated retrospectively. Genetic analysis with comparative genomic hybridization (CGH) and a family pedigree was obtained from the proband.

RESULTS

A 3-year-old girl with a history of an atrial septal defect, a horseshoe kidney and global developmental delay was presented. Ophthalmic examination revealed bilateral iris coloboma, bilateral choroidal-retinal coloboma, and left-sided microphthalmia. Subsequent oligonucleotide-based array CGH revealed two different sites of duplication and deletion on 9p (9p24.3 (209020_1143516)x1, 9p24.3p24.1 (1158662_6395264)x3).

CONCLUSION

We present the first case of MAC spectrum disorder that is related to 9p deletion and duplication. The link between the associated genetic abnormality and the phenotypic features is yet to be established. Duplication of JAK2 gene, which is within the same region of abnormalities, may have potentiated the development of MAC spectrum disease.

Disorders of Sex Development-Novel Regulators, Impacts on Fertility, and Options for Fertility Preservation

Disorders (or differences) of sex development (DSD) are a heterogeneous group of congenital conditions with variations in chromosomal, gonadal, or anatomical sex. Impaired gonadal development is central to the pathogenesis of the majority of DSDs and therefore a clear understanding of gonadal development is essential to comprehend the impacts of these disorders on the individual, including impacts on future fertility. Gonadal development was traditionally considered to involve a primary 'male' pathway leading to testicular development as a result of expression of a small number of key testis-determining genes. However, it is increasingly recognized that there are several gene networks involved in the development of the bipotential gonad towards either a testicular or ovarian fate. This includes genes that act antagonistically to regulate gonadal development. This review will highlight some of the novel regulators of gonadal development and how the identification of these has enhanced understanding of gonadal development and the pathogenesis of DSD. We will also describe the impact of DSDs on fertility and options for fertility preservation in this context.

Analysis of CDKN1C in fetal growth restriction and pregnancy loss

Background: Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a key negative regulator of cell growth encoded by a paternally imprinted/maternally expressed gene in humans. Loss-of-function variants in CDKN1C are associated with an overgrowth condition (Beckwith-Wiedemann Syndrome) whereas "gain-of-function" variants in CDKN1C that increase protein stability cause growth restriction as part of IMAGe syndrome ( Intrauterine growth restriction, Metaphyseal dysplasia, Adrenal hypoplasia and Genital anomalies). As three families have been reported with CDKN1C mutations who have fetal growth restriction (FGR)/Silver-Russell syndrome (SRS) without adrenal insufficiency, we investigated whether pathogenic variants in CDKN1C could be associated with isolated growth restriction or recurrent loss of pregnancy. Methods: Analysis of published literature was undertaken to review the localisation of variants in CDKN1C associated with IMAGe syndrome or fetal growth restriction. CDKN1C expression in different tissues was analysed in available RNA-Seq data (Human Protein Atlas). Targeted sequencing was used to investigate the critical region of CDKN1C for potential pathogenic variants in SRS (n=66), FGR (n=37), DNA from spontaneous loss of pregnancy (n= 22) and women with recurrent miscarriages (n=78) (total n=203). Results: All published single nucleotide variants associated with IMAGe syndrome are located in a highly-conserved "hot-spot" within the PCNA-binding domain of CDKN1C between codons 272-279. Variants associated with familial growth restriction but normal adrenal function currently affect codons 279 and 281. CDKN1C is highly expressed in the placenta compared to adult tissues, which may contribute to the FGR phenotype and supports a role in pregnancy maintenance. In the patient cohorts studied no pathogenic variants were identified in the PCNA-binding domain of CDKN1C. Conclusion: CDKN1C is a key negative regulator of growth. Variants in a very localised "hot-spot" cause growth restriction, with or without adrenal insufficiency. However, pathogenic variants in this region are not a common cause of isolated fetal growth restriction phenotypes or loss-of-pregnancy/recurrent miscarriages.

Analysis of CDKN1C in fetal growth restriction and pregnancy loss

Background: Cyclin-dependent kinase inhibitor 1C (CDKN1C) is a key negative regulator of cell growth encoded by a paternally imprinted/maternally expressed gene in humans. Loss-of-function variants in CDKN1C are associated with an overgrowth condition (Beckwith-Wiedemann Syndrome) whereas "gain-of-function" variants in CDKN1C that increase protein stability cause growth restriction as part of IMAGe syndrome ( Intrauterine growth restriction, Metaphyseal dysplasia, Adrenal hypoplasia and Genital anomalies). As two families have been reported with CDKN1C mutations who have fetal growth restriction (FGR)/Silver-Russell syndrome (SRS) without adrenal insufficiency, we investigated whether pathogenic variants in CDKN1C could be associated with isolated growth restriction or recurrent loss of pregnancy. Methods: Analysis of published literature was undertaken to review the localisation of variants in CDKN1C associated with IMAGe syndrome or fetal growth restriction. CDKN1C expression in different tissues was analysed in available RNA-Seq data (Human Protein Atlas). Targeted sequencing was used to investigate the critical region of CDKN1C for potential pathogenic variants in SRS (n=58), FGR (n=26), DNA from spontaneous loss of pregnancy (n= 21) and women with recurrent miscarriages (n=71) (total n=176). Results: All published single nucleotide variants associated with IMAGe syndrome are located in a highly-conserved "hot-spot" within the PCNA-binding domain of CDKN1C between codons 272-279. Variants associated with familial growth restriction but normal adrenal function currently affect codons 279 and 281. CDKN1C is highly expressed in the placenta compared to adult tissues, which may contribute to the FGR phenotype and supports a role in pregnancy maintenance. In the patient cohorts studied no pathogenic variants were identified in the PCNA-binding domain of CDKN1C. Conclusion: CDKN1C is a key negative regulator of growth. Variants in a very localised "hot-spot" cause growth restriction, with or without adrenal insufficiency. However, pathogenic variants in this region are not a common cause of isolated fetal growth restriction phenotypes or loss-of-pregnancy/recurrent miscarriages.