Genetic disruption of the oncogenic HMGA2-PLAG1-IGF2 pathway causes fetal growth restriction.

PurposeFetal growth is a complex process involving maternal, placental and fetal factors. The etiology of fetal growth retardation remains unknown in many cases. The aim of this study is to identify novel human mutations and genes related to Silver-Russell syndrome (SRS), a syndromic form of fetal growth retardation, usually caused by epigenetic downregulation of the potent fetal growth factor IGF2.MethodsWhole-exome sequencing was carried out on members of an SRS familial case. The candidate gene from the familial case and two other genes were screened by targeted high-throughput sequencing in a large cohort of suspected SRS patients. Functional experiments were then used to link these genes into a regulatory pathway.ResultsWe report the first mutations of the PLAG1 gene in humans, as well as new mutations in HMGA2 and IGF2 in six sporadic and/or familial cases of SRS. We demonstrate that HMGA2 regulates IGF2 expression through PLAG1 and in a PLAG1-independent manner.ConclusionGenetic defects of the HMGA2-PLAG1-IGF2 pathway can lead to fetal and postnatal growth restriction, highlighting the role of this oncogenic pathway in the fine regulation of physiological fetal/postnatal growth. This work defines new genetic causes of SRS, important for genetic counseling.

Practice patterns for chronic hypoparathyroidism: data from patients and physicians in France.

Context: Recent guidelines have provided recommendations for the care of patients with chronic hypoparathyroidism. Very little is known about actual physicians' practices or their adherence to such guidelines. Objective: To describe the physicians' practice patterns and their compliance with international guidelines. Design: The cohort studies included were Épi-Hypo (118 physicians and 107 patients, from September 2016 to December 2019) and ePatients (110 patients, November 2019). Methods: Internet-based cohorts involving all settings at a nationwide level (France). Participants were (i) physicians treating patients with chronic hypoparathyroidism and patients with chronic hypoparathyroidism either participating in the (ii) Épi-Hypo study (Épi-Hypo 2019 patients), or (iii) Hypoparathyroidism France, the national representative association (ePatients). Results: The physicians' specialties were mainly endocrinology (61%), nephrology (28%), family medicine (2.5%), pediatrics (2.5%), rheumatology (2%), or miscellaneous (4%) and 45% were practicing in public universities. The median number of pharmaceutical drug classes prescribed was three per patient. The combination of active vitamin D and calcium salt was given to 59 and 58% of ePatients and Épi-Hypo 2019 patients, respectively. Eighty-five percent of ePatients and 87% of physicians reported monitoring plasma calcium concentrations at a steady state at least twice a year. In 32 and 26% of cases, respectively, ePatients and physicians reported being fully in accordance with international guidelines that recommend targeting symptoms, plasma calcium and phosphate values, and urine calcium excretion. Conclusions: The care of patients with chronic hypoparathyroidism involves physicians with very different practices, so guidelines should include and target other specialists as well as endocrinologists. Full adherence to the guidelines is low in France.

Presenting features and molecular genetics of primary hyperparathyroidism in the paediatric population.

AIM: To describe the presenting features and molecular genetics of primary hyperparathyroidism (PHPT) in the paediatric population. METHODS: Retrospective study of 63 children diagnosed with primary PHPT from 1998 to 2018. RESULTS: Compared to older children, infants were often asymptomatic (54% vs 15%, P = 0.002) with a milder form of PHPT. When symptomatic, children and adolescents mostly presented with non-specific complaints such as asthenia, depression, weight loss, vomiting or abdominal pain. A genetic cause of PHPT was identified in about half of this cohort (52%). The infancy period was almost exclusively associated with mutation in genes involved in the calcium-sensing receptor (CaSR) signalling pathway (i.e. CaSR and AP2S1 genes, 'CaSR group'; 94% of infants with mutations) whereas childhood and adolescence were associated with mutation in genes involved in parathyroid cell proliferation (i.e. MEN1, CDC73, CDKN1B and RET genes, 'cell proliferation group'; 69% of children and adolescents with mutations). Although serum calcium levels did not differ between the two groups (P = 0.785), serum PTH levels and the urinary calcium/creatinine ratio were significantly higher in 'cell proliferation group' patients compared to those in the 'CaSR group' (P = 0.001 and 0.028, respectively). CONCLUSION: Although far less common than in adults, PHPT can develop in children and is associated with significant morbidity. Consequently, this diagnosis should be considered in children with non-specific complaints and lead to monitoring of mineral homeostasis parameters. A genetic cause of PHPT can be identified in about half of these patients.

Demographic Characteristics, Risk Factors, and Presenting Features of Children with Symptomatic Nutritional Rickets: A French Series.

AIM: To describe the demographic characteristics, risk factors, and presenting features of children with symptomatic nutritional rickets in France. METHODS: This is a retrospective study of 38 children diagnosed with nutritional rickets from 1998 to 2019. RESULTS: We observed a higher frequency of rickets in males (74 vs. 26%), in young children (median age at diagnosis: 23 months; 82% were younger than 5 years), and in children with a non-Caucasian ethnic background (89%). Most children were exclusively breastfed (78%) without adequate vitamin D supplementation (89%). The most common presentations were bowed legs (63%), hypocalcemic seizures (21%), and growth retardation (11%). Approximately half (62%) of the children were hypocalcemic. The children presenting with hypocalcemic seizures were significantly younger (0.8 vs. 2.2 years; p = 0.041) and had lower total serum calcium levels (1.44 vs. 2.17 mmol/L; p < 0.0001), higher phosphatemia (1.43 vs. 1.23 mmol/L; p = 0.020), and lower 25-hydroxy vitamin D levels (3 vs. 7 ng/mL; p = 0.020) but similar parathyroid hormone levels (357 vs. 289 ng/mL; p = 0.940) compared to rickets cases who did not experience hypocalcemic seizures. A dilated cardiomyopathy was detected in 14% of the children who had undergone echocardiography. CONCLUSION: Nutritional rickets remains endemic in the pediatric population and its most severe forms can have life-threatening sequelae. Health practitioners need to be cognizant of these facts to raise awareness and screen high-risk populations.

Kallmann syndrome: mutations in the genes encoding prokineticin-2 and prokineticin receptor-2.

Kallmann syndrome combines anosmia, related to defective olfactory bulb morphogenesis, and hypogonadism due to gonadotropin-releasing hormone deficiency. Loss-of-function mutations in KAL1 and FGFR1 underlie the X chromosome-linked form and an autosomal dominant form of the disease, respectively. Mutations in these genes, however, only account for approximately 20% of all Kallmann syndrome cases. In a cohort of 192 patients we took a candidate gene strategy and identified ten and four different point mutations in the genes encoding the G protein-coupled prokineticin receptor-2 (PROKR2) and one of its ligands, prokineticin-2 (PROK2), respectively. The mutations in PROK2 were detected in the heterozygous state, whereas PROKR2 mutations were found in the heterozygous, homozygous, or compound heterozygous state. In addition, one of the patients heterozygous for a PROKR2 mutation was also carrying a missense mutation in KAL1, thus indicating a possible digenic inheritance of the disease in this individual. These findings reveal that insufficient prokineticin-signaling through PROKR2 leads to abnormal development of the olfactory system and reproductive axis in man. They also shed new light on the complex genetic transmission of Kallmann syndrome.

Aberrant Splicing Is the Pathogenicity Mechanism of the p.Glu314Lys Variant in CYP11A1 Gene.

Context: The cholesterol side chain cleavage enzyme (CYP11A1) catalyzes the conversion of cholesterol to pregnenolone, the first rate-limiting step of steroidogenesis. CYP11A1 mutations are associated with primary adrenal insufficiency (PAI) as well as disorders of sex development (DSD) in 46,XY patients. Objective: To define the pathogenicity mechanism for the p.Glu314Lys variant, previously reported, and found in four additional patients with CYP11A1 deficiency. Subjects and Methods: DNA of four patients presenting with delayed PAI and/or 46,XY DSD were studied by Sanger or Massively Parallel sequencing. Three CYP11A1 mutations were characterized in vitro and in silico, and one by mRNA analysis on testicular tissue. Results: All patients were compound heterozygous for the previously described p.Glu314Lys variant. In silico studies predicted this mutation as benign with no effect on splicing but mRNA analysis found that it led to incomplete exon 5 skipping. This mechanism was confirmed by minigene experiment. The protein carrying this mutation without exon skipping should conserve almost normal activity, according to in vitro studies. Two other mutations found in trans, the p.Arg120Gln and p.Arg465Trp, had similar activity compared to negative control, consistent with the in silico studies. Conclusions: We provide biological proof that the p. Glu314Lys variant is pathogenic due to its impact on splicing and seems responsible for the moderate phenotype of the four patients reported herein. The present study highlights the importance of considering the potential effect of a missense variant on splicing when it is not predicted to be disease causing.

P450 Oxidoreductase Deficiency: Loss of Activity Caused by Protein Instability From a Novel L374H Mutation.

CONTEXT: P450 oxidoreductase (POR) is required for the activities of steroid-metabolizing cytochrome P450 enzymes in the endoplasmic reticulum. POR deficiency (PORD) is a form of congenital adrenal hyperplasia. Objective and Aim: Enzymatic and structural analysis of a novel L374H POR mutation from a patient with 46,XX disorder of sexual development. Design, Setting, Patient, and Intervention: The patient was a 46,XX girl with nonconsanguineous Turkish parents. She had virilized external genitalia at birth, a uterus and ovaries, and no sign of Antley-Bixler syndrome. The initial diagnosis was CYP21A2 deficiency with no mutations in CYP21A2, but POR mutations were found. Functional testing was done after producing recombinant POR proteins for analyzing enzymatic and structural properties. MAIN OUTCOME: Novel mutations were causing severe loss of POR activities for metabolism of steroids and small molecules. RESULTS: The L374H mutation reduced activities by 80% in cytochrome c, 97% in thiazolyl blue tetrazolium bromide, and 86% in ferricyanide reduction assays. The catalytic efficiency of the 17 α-hydroxylation of progesterone and the 17,20-lyase reaction of 17-OH pregnenolone was decreased by 87 and 90%, respectively; 21-hydroxylation of progesterone was decreased by 96%, and androstenedione aromatization was decreased by 90%. Analysis of the mutant structure by molecular dynamics simulations revealed structural instability. Flavin release and fast proteolysis assays showed that the L374H mutant is less stable than wild-type POR, confirming the bioinformatics prediction. CONCLUSIONS: This is the first report of a mutation causing PORD by affecting protein stability that causes severe reduction in POR activities. Detailed characterization of individual mutations in POR is required for understanding novel molecular mechanisms causing PORD.

Treatment experience and long-term follow-up data in two severe neonatal hyperparathyroidism cases.

The calcium sensing receptor (CASR) is expressed most abundantly in the parathyroid glands and the kidney. CASR regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. Inactivating mutations in the CASR gene may result in disorders of calcium homeostasis manifesting as familial benign hypocalciuric hypercalcemia (FBHH) and neonatal severe hyperparathyroidsm (NSHPT). Two cases were referred with severe hypercalcemia in the neonatal period. Laboratory evaluation revealed severe hypercalcemia and elevated PTH. The parents also had mild hypercalcemia. The serum calcium level did not normalize with conventional hypercalcemia treatment and there was also no response to cinacalcet in case 1. Total parathyroidectomy was performed when the patient was 70 days old. Genetic analysis revealed a novel homozygous p.Arg544* mutation in the CASR gene. Case 2 underwent total parathyroidectomy and autoimplantation when she was 97 days old, but the parathyroid gland implanted into the forearm was removed 27 days later because the hypercalcemia continued. Genetic evaluation revealed a novel homozygous p.Pro682Leu mutation with normal anthropometric measurements. The neurological development is consistent with age in both cases while case 2 has mild mental retardation. No bone deformity or fracture is present in either case and normocalcemia is ensured with calcitriol in both cases.

Late prenatal dexamethasone and phenotype variations in 46,XX CAH: concerns about current protocols and benefits for surgical procedures.

OBJECTIVE: To describe the action of prenatal dexamethasone (PreDex) on the anatomy of female congenital adrenal hyperplasia (CAH) genitalia when started at later stages of gestation. MATERIALS AND METHODS: Our group follows a large cohort of French CAH patients who underwent PreDex therapy, of whom 258 were recently reported. Four 46,XX patients with a delayed PreDex treatment presented with a virilized genitalia and required surgical reconstruction. This is a retrospective report on genital phenotyping at the time of surgery of these four patients who began PreDex therapy at 8, 12, 20, and 28 weeks of gestation. RESULTS: Although this series is limited in number, the anatomical description of the length of the genital tubercle, the height of the urethra-vaginal confluence, and the degree of fusion of the genital folds seems to be dependent upon the starting date of PreDex. Most PreDex treatments prescribed up to now have covered the full duration of gestation. CONCLUSIONS: Our findings suggest that PreDex therapy could be limited to the period of the partitioning window. It is hoped that further prospective multicentric clinical studies will obtain ethical approval in order to elucidate the place and protocols of PreDex therapy in the management of CAH.

Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity.

OBJECTIVE: Gain-of-function mutations of the calcium-sensing receptor (CASR) gene have been identified in patients with sporadic or familial autosomal dominant hypocalcemia (ADH). Inactivating mutations of the CASR gene cause familial hypocalciuric hypercalcemia (FHH). Here, we report two novel CASR mutations affecting the same amino acid (p.N802); one causes ADH and the other atypical FHH. PATIENTS AND METHODS: The first patient, an 11-year-old girl suffering from hypocalcemia, developed nephrocalcinosis when she was only 5 years old. The second patient is a 30-year-old woman who presented with mild hypercalcemia. PCR amplification of CASR coding exons and direct sequencing of PCR products were used to identify mutations. Site-directed mutagenesis was used to generate mutated CASR cDNAs in an expression plasmid. Using the MAPK assay system and transient transfection of Cos-7 cells with wild-type (WT) and mutated CASR, we studied the responses of these mutated receptors to extracellular Ca(2+) and to the negative allosteric CASR modulator, NPS2143. RESULTS: Two heterozygous missense mutations (p.N802I and p.N802S) affecting a residue in the sixth transmembrane domain of CASR were identified. In functional tests, the response of the p.N802S mutant to calcium was typical of an inactivating mutation. However, the p.N802I mutant had 70% of the maximally stimulated WT receptor activity even in the absence of extracellular calcium. This constitutive activity was only partially inhibited by the inhibitor, NPS2143. CONCLUSIONS: The asparagine at amino acid position 802 appears to be essential for the activity of the CASR protein and is implicated in the mechanism of CASR signaling.

A comparative phenotypic study of kallmann syndrome patients carrying monoallelic and biallelic mutations in the prokineticin 2 or prokineticin receptor 2 genes.

CONTEXT: Both biallelic and monoallelic mutations in PROK2 or PROKR2 have been found in Kallmann syndrome (KS). OBJECTIVE: The objective of the study was to compare the phenotypes of KS patients harboring monoallelic and biallelic mutations in these genes. DESIGN AND PATIENTS: We studied clinical and endocrine features that reflect the functioning of the pituitary-gonadal axis, and the nonreproductive phenotype, in 55 adult KS patients (42 men and 13 women), of whom 41 had monoallelic mutations and 14 biallelic mutations in PROK2 or PROKR2. RESULTS: Biallelic mutations were associated with more frequent cryptorchidism (70% vs. 34%, P < 0.05) and microphallus (90% vs. 28%, P < 0.001) and lower mean testicular volume (1.2 +/- 0.4 vs. 4.5 +/- 6.0 ml; P < 0.01) in male patients. Likewise, the testosterone level as well as the basal FSH level and peak LH level under GnRH-stimulation were lower in males with biallelic mutations (0.2 +/- 0.1 vs. 0.7 +/- 0.8 ng/ml; P = 0.05, 0.3 +/- 0.1 vs. 1.8 +/- 3.0 IU/liter; P < 0.05, and 0.8 +/- 0.8 vs. 5.2 +/- 5.5 IU/liter; P < 0.05, respectively). Nonreproductive, nonolfactory anomalies were rare in both sexes and were never found in patients with biallelic mutations. The mean body mass index of the patients (23.9 +/- 4.2 kg/m(2) in males and 26.3 +/- 6.6 kg/m(2) in females) did not differ significantly from that of gender-, age-, and treatment-matched KS individuals who did not carry a mutation in PROK2 or PROKR2. Finally, circadian cortisol levels evaluated in five patients, including one with biallelic PROKR2 mutations, were normal in all cases. CONCLUSION: Male patients carrying biallelic mutations in PROK2 or PROKR2 have a less variable and on average a more severe reproductive phenotype than patients carrying monoallelic mutations in these genes. Nonreproductive, nonolfactory clinical anomalies associated with KS seem to be restricted to patients with monoallelic mutations.