HNF1A gene mutations and premature ovarian failure (POF): evidence from a clinical paradigm combining MODY 3 and POF

Premature ovarian failure (POF) defines the occurrence of ovarian failure prior to the age of 40. It occurs in one out of 100 women but is very rare before age 20 (1:10,000). Maturity-onset diabetes of the young (MODY), caused by mutations in the HNF1A gene, is also a rare disorder; all types of MODY account for 1-2% of adult diabetic cases. These two rare nosologic entities coexisted in an adolescent girl evaluated for delayed puberty. Although this combination could represent a chance association, an interrelation might exist. We examined HNF1A expression in human fetal and adult ovaries by immunohistochemistry using a polyclonal HNF1A antibody. HNF1A protein was expressed in both the fetal and adult human ovaries. Based on these findings, we hypothesize that HNF1A participates in ovarian organogenesis and/or function and that mutations in the HNF1A gene might represent another molecular defect causing POF, possibly in combination with other genetic factors. The study underlines the importance of rare clinical paradigms in leading the way to elucidation of the pathogenetic mechanisms of rare diseases.

USP13 genetics and expression in a family with thyroid cancer

PURPOSE

Papillary thyroid carcinoma (PTC) is the most common type of thyroid carcinoma and its incidence has greatly increased in the last 30 years. Ubiquitin-specific protease 13 (USP13) is a class of deubiquitinating enzymes (DUBs) and plays an important role in cellular functions such as cell cycle regulation, DNA damage repair, and different cell signaling pathways. Studies regarding the role of USP13 in cancer development and progression are divergent and there are no previous data regarding the role of USP13 gene in PTCs. In this study, we investigated the genetic cause of PTC diagnosed in multiple members of a Brazilian family.

METHODS

Whole exome sequencing (WES) was performed to identify the genetic cause of PTC. Cycloheximide chase assay and clonogenic assay were performed to study USP13 stability and function in vitro.

RESULTS

WES analysis identified a heterozygous missense variant c.1483G > A (p.V495M) in the USP13 gene that fully segregates with the disease. In silico modeling suggests that this variant may cause protein structural perturbations. USP13 overexpression increased the potential of a single cell to form colonies. The USP13 c.1483G > A variant enhanced the effects seen in USP13 overexpression and preserved protein stability for longer hours compared to the non-mutated USP13 protein.

CONCLUSION

Our study suggests that USP13 overexpression may play a role in tumorigenesis of PTCs; and that the USP13 p.V495M (c.1483G > A) variant enhances USP13 estability.

Kisspeptin deficiency leads to abnormal adrenal glands and excess steroid hormone secretion

Knockout mice for the kisspeptin receptor, Kiss1r (Kiss1r-/-) and its ligand kisspeptin, Kiss1 (Kiss1-/-) replicate the phenotype of isolated hypogonadotropic hypogonadism (IHH) associated with variants of these genes in humans. A recent report suggests that kisspeptin may be involved in human fetal adrenocortical development and function. Herein, we characterized the adrenal function and morphology in Kiss1-/- mice that do not go through normal puberty. Two fetal markers were expressed in eosinophilic cells potentially derived from the X-zone that should disappear at puberty in male mice and during the first pregnancy in female animals. Although the hypercorticosteronism observed in Kiss1-/- females corrected overtime, hyperaldosteronism persisted at 14 months and correlated with the overexpression of Star. To determine if KISS1 and KISS1R genes are involved in the development of primary aldosteronism (PA) and hypercortisolism [Cushing's syndrome (CS)] in humans, we sequenced these 2 genes in 65 patients with PA and/or CS. Interestingly, a patient with CS presented with a germline KISS1 variant (p.H90D, rs201073751). We also found three rare variants in the KISS1R gene in three patients with PA: p.C95W (rs141767649), p.A189T (rs73507527) and p.R229R (rs115335009). The two missense variants have been previously associated with IHH. Our findings suggest that KISS1 may play a role in adrenal function in mice and possibly adrenocortical steroid hormone secretion in humans, beyond its recently described role in human fetal adrenocortical development.

Variants in PRKAR1B cause a neurodevelopmental disorder with autism spectrum disorder, apraxia, and insensitivity to pain

PURPOSE

We characterize the clinical and molecular phenotypes of six unrelated individuals with intellectual disability and autism spectrum disorder who carry heterozygous missense variants of the PRKAR1B gene, which encodes the R1β subunit of the cyclic AMP-dependent protein kinase A (PKA).

METHODS

Variants of PRKAR1B were identified by single- or trio-exome analysis. We contacted the families and physicians of the six individuals to collect phenotypic information, performed in vitro analyses of the identified PRKAR1B-variants, and investigated PRKAR1B expression during embryonic development.

RESULTS

Recent studies of large patient cohorts with neurodevelopmental disorders found significant enrichment of de novo missense variants in PRKAR1B. In our cohort, de novo origin of the PRKAR1B variants could be confirmed in five of six individuals, and four carried the same heterozygous de novo variant c.1003C>T (p.Arg335Trp; NM_001164760). Global developmental delay, autism spectrum disorder, and apraxia/dyspraxia have been reported in all six, and reduced pain sensitivity was found in three individuals carrying the c.1003C>T variant. PRKAR1B expression in the brain was demonstrated during human embryonal development. Additionally, in vitro analyses revealed altered basal PKA activity in cells transfected with variant-harboring PRKAR1B expression constructs.

CONCLUSION

Our study provides strong evidence for a PRKAR1B-related neurodevelopmental disorder.

The PRKAR1B p.R115K Variant is Associated with Lipoprotein Profile in African American Youth with Metabolic Challenges

Context

High childhood obesity rates coincide with increased incidence of nonalcoholic fatty liver disease (NAFLD) and other comorbidities. Understanding the genetics of susceptibility to obesity and its comorbidities could guide intervention. The cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) signaling pathway regulates energy balance, glucose homeostasis, and lipid metabolism.

Objective

We hypothesized that PKA-related gene variants may be associated with obesity or associated metabolic conditions.

Methods

We included 457 youths from the Yale Obesity Clinic into the Pathogenesis of Youth-Onset Diabetes cohort (NCT01967849); a variety of clinical tests were performed to characterize NAFLD. Exon sequencing of 54 PKA pathway genes was performed. Variants were confirmed by Sanger sequencing. Clinical data were analyzed, correcting for NAFLD status and body mass index z-score with adjustments for multiple comparisons. Fluorescence resonance energy transfer (FRET) and PKA enzymatic assays were performed in HEK293 cells transfected with the PRKAR1B p.R115K construct. In silico structural analysis for this variant was done.

Results

We identified the variant PRKAR1B p.R115K in 4 unrelated, African American patients. Analyses compared this variant group to other African American patients in the cohort. PRKAR1B p.R115K was associated with favorable circulating lipoprotein levels. Analysis of FRET and PKA enzymatic assay showed stronger interaction between the R1β mutant and PKA catalytic subunit Cα and decreased basal PKA activity compared with the wildtype (P < .0001). Structural analysis revealed that p.R115K may hinder conformational changes resulting from cAMP binding at cAMP binding domain A.

Conclusion

Data suggest PRKAR1B p.R115K affects cAMP signaling and may favorably modulate lipoprotein profile in African American youth, protecting them from some adverse metabolic outcomes.

Carney Triad, Carney-Stratakis Syndrome, 3PAS and Other Tumors Due to SDH Deficiency

Succinate dehydrogenase (SDH) is a key respiratory enzyme that links Krebs cycle and electron transport chain and is comprised of four subunits SDHA, SDHB, SDHC and SDHD. All SDH-deficient tumors are caused by or secondary to loss of SDH activity. As many as half of the familial cases of paragangliomas (PGLs) and pheochromocytomas (PHEOs) are due to mutations of the SDHx subunits. Gastrointestinal stromal tumors (GISTs) associated with SDH deficiency are negative for KIT/PDGFRA mutations and present with distinctive clinical features such as early onset (usually childhood or adolescence) and almost exclusively gastric location. SDH-deficient GISTs may be part of distinct clinical syndromes, Carney-Stratakis syndrome (CSS) or dyad and Carney triad (CT). CSS is also known as the dyad of GIST and PGL; it affects both genders equally and is inherited in an autosomal dominant manner with incomplete penetrance. CT is a very rare disease; PGL, GIST and pulmonary chondromas constitute CT which shows female predilection and may be a mosaic disorder. Even though there is some overlap between CT and CSS, as both are due to SDH deficiency, CSS is caused by inactivating germline mutations in genes encoding for the SDH subunits, while CT is mostly caused by a specific pattern of methylation of the SDHC gene and may be due to germline mosaicism of the responsible genetic defect.

PRKACB variants in skeletal disease or adrenocortical hyperplasia: effects on protein kinase A

Genetic variants in components of the protein kinase A (PKA) enzyme have been associated with various defects and neoplasms in the context of Carney complex (CNC) and in isolated cases, such as in primary pigmented nodular adrenocortical disease (PPNAD), cortisol-producing adrenal adenomas (CPAs), and various cancers. PRKAR1A mutations have been found in subjects with impaired cAMP-dependent signaling and skeletal defects; bone tumors also develop in both humans and mice with PKA abnormalities. We studied the PRKACB gene in 148 subjects with PPNAD and related disorders, who did not have other PKA-related defects and identified two subjects with possibly pathogenic PRKACB gene variants and unusual bone and endocrine phenotypes. The first presented with bone and other abnormalities and carried a de novo c.858_860GAA (p.K286del) variant. The second subject carried the c.899C>T (p.T300M or p.T347M in another isoform) variant and had a PPNAD-like phenotype. Both variants are highly conserved in the PRKACB gene. In functional studies, the p.K286del variant affected PRKACB protein stability and led to increased PKA signaling. The p.T300M variant did not affect protein stability or response to cAMP and its pathogenicity remains uncertain. We conclude that PRKACB germline variants are uncommon but may be associated with phenotypes that resemble those of other PKA-related defects. However, detailed investigation of each variant is needed as PRKACB appears to be only rarely affected in these conditions, and variants such as p.T300M maybe proven to be clinically insignificant, whereas others (such as p.K286del) are clearly pathogenic and may be responsible for a novel syndrome, associated with endocrine and skeletal abnormalities.

Genomic and sequence variants of protein kinase A regulatory subunit type 1β (PRKAR1B) in patients with adrenocortical disease and Cushing syndrome

Purpose:

Protein kinase A (PKA) subunit defects (in PRKAR1A and PRKACA) are known to contribute to adrenal tumor pathogenesis. We studied the PRKAR1B gene for any genetic changes in bilateral adrenocortical hyperplasia (BAH) and cortisol-producing adrenal adenomas (CPA).

Methods:

Exome sequencing and PRKAR1B copy number variant (CNV) analysis were performed in 74 patients with BAH and 21 with CPA. PKA activity was studied in tumors with defects; sequence variants were investigated in vitro.

Results:

Three PRKAR1B germline variants (p.I40V, p.A67V, p.A300T) were identified among 74 patients with BAH. PRKAR1B copy number gains (CNG) were found in 3 of 21 CPAs, one in a tumor carrying a somatic PRKACA “hot-spot” pathogenic variant p.L206R. CPAs bearing PRKAR1B CNGs showed higher PRKAR1B mRNA levels and reduced PKA activity. Baseline PKA activity was also decreased for p.A67V and p.A300T in vitro, and mutant PRKAR1β bound PRKACα in FRET recordings of co-transfected HEK293 cells stronger than normal.

Conclusion:

PRKAR1B is yet another PKA subunit that may potentially contribute to adrenal tumor formation. Its involvement in adrenocortical disease may be different from that of other subunits, because PRKAR1B variants and PRKAR1B CNG were associated with decreased (rather than increased) overall PKA activity in vitro.

ARMC5 variants in PRKAR1A-mutated patients modify cortisol levels and Cushing's syndrome

Mutations in the protein kinase A (PKA) regulatory subunit type 1A (PRKAR1A) and armadillo repeat-containing 5 (ARMC5) genes cause Cushing's syndrome (CS) due to primary pigmented nodular adrenocortical disease (PPNAD) and primary bilateral macronodular adrenocortical hyperplasia (PBMAH), respectively. Between the two genes, ARMC5 is highly polymorphic with several variants in the population, whereas PRKAR1A has very little, if any, non-pathogenic variation in its coding sequence. We tested the hypothesis that ARMC5 variants may affect the clinical presentation of PPNAD and CS among patients with PRKAR1A mutations. In this study, 91 patients with PPNAD due to PRKAR1A mutations were tested for abnormal cortisol secretion or CS and for ARMC5 sequence variants. Abnormal cortisol secretion was present in 71 of 74 patients with ARMC5 variants, whereas 11 of 17 patients negative for ARMC5 variants did not have hypercortisolemia. The presence of ARMC5 variants was a statistically strong predictor of CS among patients with PRKAR1A mutations (P < 0.001). Among patients with CS due to PPNAD, ARMC5 variants were associated with lower cortisol levels at baseline (P = 0.04) and after high dose dexamethasone administration (P = 0.02). The ARMC5 p.I170V variant increased ARMC5 protein accumulation in vitro and decreased viability of NCI-H295 cells (but not HEK 293T cells). PPNAD tissues with ARMC5 variants showed stronger ARMC5 protein expression than those that carried a normal ARMC5 sequence. Taken together, our results suggest that ARMC5 variants among patients with PPNAD due to PRKAR1A defects may play the role of a genetic modifier for the presence and severity of hypercortisolemia.

OR24-06 USP8 Genetic Variants May Contribute to the Development of Bilateral Adrenal Hyperplasia and ACTH-Independent Cushing Syndrome

Background: Bilateral adrenocortical hyperplasias (BAHs), including primary pigmented nodular adrenocortical disease (PPNAD), isolated micronodular adrenocortical disease (iMAD) and primary macronodular adrenocortical hyperplasia (PMAH), are rare causes of ACTH-independent Cushing syndrome (CS). PPNAD and iMAD usually present in children or adolescents as multiple small (&lt;1cm), cortisol-producing adrenocortical nodules. On the other hand, PMAH is most frequently identified in older patients with multiple large adrenal nodules. Most patients with PPNAD have PRKAR1A mutations whereas patients with PMAH may harbor variants in other genes (ARMC5, MC2R, GNAS, APC, MEN1). Even though several genes have been associated with ACTH-independent CS, there are still cases that the genetic cause has not been elucidated.

Clinical cases: Herein, we present two unrelated patients with ACTH-independent CS that harbor USP8 gene variants. USP8 is mainly known for being mutated in Cushing disease but as a deubiquitinase it may be involved into the Wnt/β-Catenin signaling pathway.

The first patient was diagnosed with BAH on prenatal ultrasound (26 gestational week) and subsequently required bilateral adrenalectomy for CS as she had virilization, hirsutism, hypertension and cardiac hypertrophy 9 weeks old. Adrenalectomy revealed that she had iMAD. She also presented with hemihypertrophy of the right leg, labia and mild newborn hypoglycemia, however she was negative for Beckwith-Wiedemann mutation. Gene analysis of PRKAR1A did not reveal any mutations. After whole exome sequencing (WES), we found a novel heterozygous USP8 variant (c.1387_1393delinsT, p.Ala463_Ile465delinsPhe) at germline level and loss of heterozygosity (LOH) at tumor level. Immunohistochemistry showed significantly lower expression of USP8 protein in both of her adrenals compared to a control tissue.

The second case is a 59-year old female with osteoporosis who failed to suppress cortisol levels after low dose dexamethasone administration. MRI revealed an adenoma on the right adrenal (2.6cm). She underwent right adrenalectomy and was found to have PMAH. We performed WES in germline level and we detected a novel heterozygous missense USP8 variant (c.287A&gt;G, p.Lys96Arg) that is present also at tumor level. Immunohistochemistry showed significantly lower expression of USP8 protein in her adrenal tumor compared to the control tissue. No LOH was identified.

Conclusion: This is the first report of the association of USP8 in ACTH-independent CS and the preliminary findings support UPS8 involvement in the development of adrenocortical disease. We are currently performing further in vitro studies to evaluate the effect of these two USP8 variants into the canonical Wnt pathway which is commonly involved in adrenocortical disorders.

SGPL1 Deficiency: A Rare Cause of Primary Adrenal Insufficiency

CONTEXT

Multiple autosomal recessive genes have been etiologically linked to primary adrenal insufficiency (PAI). Recently, sphingosine-1-phosphate lyase 1 (SGPL1) gene mutations were recognized as a cause of steroid-resistant nephrotic syndrome type 14 (NPHS14), a sphingolipidosis with multisystemic manifestations, including PAI.

OBJECTIVE

To check if SGPL1 mutations are involved in the pathogenesis of PAI in patients who do not exhibit nephrotic syndrome.

METHODS

Sequencing of the SGPL1 gene in 21 patients with familial glucocorticoid disease or triple A syndrome.

RESULTS

We identified two missense SGPL1 variants in four patients, two of whom were first cousins. We describe in detail the proband, a boy born to Saudi Arabian consanguineous parents with a homozygous c.665G>A, p.R222Q SGPL1 variant. The patient presented with hypoglycemia and seizures at age 2 years and was ultimately diagnosed with PAI (isolated glucocorticoid deficiency). Brain MRI showed abnormalities in the basal ganglia consistent with a degenerative process albeit the patient had no neurologic symptoms.

CONCLUSIONS

New genetic causes of PAI continue to be identified. We suggest that screening for SGPL1 mutations should not be reserved only for patients with nephrotic syndrome but may also include patients with PAI who lack other clinical manifestations of NPHS14 because, in certain cases, kidney disease and accompanying features might develop. Timely diagnosis of this specific sphingolipidosis while the kidneys still function normally can lead to prompt initiation of therapy and improve outcome.

Succinate dehydrogenase (SDH) deficiency, Carney triad and the epigenome

In this report, we review the relationship between succinate dehydrogenase (SDH) deficiency and the epigenome, especially with regards to two clinical conditions. Carney triad (CT) is a very rare disease with synchronous or metachronous occurrence of at least three different tumor entities; gastric gastrointestinal stromal tumor (GIST), paraganglioma (PGL), and pulmonary chondroma. This condition affects mostly females and it is never inherited. Another disease that shares two of the tumor components of CT, namely GIST and PGL is the Carney-Stratakis syndrome (CSS) or dyad. CSS affects both genders during childhood and adolescence. We review herein the main clinical features and molecular mechanisms behind those two syndromes that share quite a bit of similarities, but one is non-hereditary (CT) whereas the other shows an autosomal-dominant, with incomplete penetrance, inheritance pattern (CSS). Both CT and CSS are caused by the deficiency of the succinate dehydrogenase (SDH) enzyme. The key difference between the two syndromes is the molecular mechanism that causes the SDH deficiency. Most cases of CT show down-regulation of SDH through site-specific hyper-methylation of the SDHC gene, whereas CSS cases carry inactivating germline mutations within one of the genes coding for the SDH subunits A, B, C, or D (SDHA, SDHB, SDHC, and SDHD). There is only partial overlap between the two conditions (there are a few patients with CT that have SDH subunit mutations) but both lead to increased methylation of the entire genome in the tumors associated with them. Other tumors (outside CT and CSS) that have SDH deficiency are associated with increased methylation of the entire genome, but only in CT there is site-specific methylation of the SDHC gene. These findings have implications for diagnostics and the treatment of patients with these, often metastatic tumors.

The E3 ubiquitin ligase Siah1 regulates adrenal gland organization and aldosterone secretion

Primary and secondary hypertension are major risk factors for cardiovascular disease, the leading cause of death worldwide. Elevated secretion of aldosterone resulting from primary aldosteronism (PA) is a key driver of secondary hypertension. Here, we report an unexpected role for the ubiquitin ligase Siah1 in adrenal gland development and PA. Siah1a-/- mice exhibit altered adrenal gland morphology, as reflected by a diminished X-zone, enlarged medulla, and dysregulated zonation of the glomerulosa as well as increased aldosterone levels and aldosterone target gene expression and reduced plasma potassium levels. Genes involved in catecholamine biosynthesis and cAMP signaling are upregulated in the adrenal glands of Siah1a-/- mice, while genes related to retinoic acid signaling and cholesterol biosynthesis are downregulated. Loss of Siah1 leads to increased expression of the Siah1 substrate PIAS1, an E3 SUMO protein ligase implicated in the suppression of LXR, a key regulator of cholesterol levels in the adrenal gland. In addition, SIAH1 sequence variants were identified in patients with PA; such variants impaired SIAH1 ubiquitin ligase activity, resulting in elevated PIAS1 expression. These data identify a role for the Siah1-PIAS1 axis in adrenal gland organization and function and point to possible therapeutic targets for hyperaldosteronism.

Medullary thyroid cancer, leukemia, mesothelioma and meningioma associated with germline APC and RASAL1 variants: a new syndrome?

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor hereditary in 35% of cases. The most common syndromic form is in the context of the multiple endocrine neoplasia type 2 (MEN 2) syndromes in association with other tumors and due to germline RET mutations. We describe a 57-year-old female patient diagnosed with sporadic MTC. The patient had a history of other neoplasias, such as acute myeloid leukemia, for which she had received chemotherapy, and two other solid tumors, peritoneal mesothelioma and meningioma. Genetic analyses were carried out including whole exome and Sanger sequencing (WES and SS) and loss-of-heterozygosity (LOH) testing for the respective loci. Immunohistochemistry (IHC) was used for the detection of proteins of interest. WES showed two germline variants in the APC and RASAL1 genes confirmed by SS. In MTC tissue only there was a RETvariant identified by SS; germline studies did not show any RETsequence changes. The pattern of tumors in this patient is unusual for either one of the APC- orRASAL1-associated neoplasms and her non-MEN 2-associated MTC contained a RET variant like other sporadic MTCs. As in other patients with more than one genetic variant predisposing to tumors, it is possible that this case represents a unique association.

Somatic USP8 Gene Mutations Are a Common Cause of Pediatric Cushing Disease

CONTEXT

Somatic mutations in the ubiquitin-specific protease 8 (USP8) gene have been recently identified as the most common genetic alteration in patients with Cushing disease (CD). However, the frequency of these mutations in the pediatric population has not been extensively assessed.

OBJECTIVE

We investigated the status of the USP8 gene at the somatic level in a cohort of pediatric patients with corticotroph adenomas.

DESIGN AND METHODS

The USP8 gene was fully sequenced in both germline and tumor DNA samples from 42 pediatric patients with CD. Clinical, biochemical, and imaging data were compared between patients with and without somatic USP8 mutations.

RESULTS

Five different USP8 mutations (three missense, one frameshift, and one in-frame deletion) were identified in 13 patients (31%), all of them located in exon 14 at the previously described mutational hotspot, affecting the 14-3-3 binding motif of the protein. Patients with somatic mutations were older at disease presentation [mean 5.1 ± 2.1 standard deviation (SD) vs 13.1 ± 3.6 years, P = 0.03]. Levels of urinary free cortisol, midnight serum cortisol, and adrenocorticotropic hormone, as well as tumor size and frequency of invasion of the cavernous sinus, were not significantly different between the two groups. However, patients harboring somatic USP8 mutations had a higher likelihood of recurrence compared with patients without mutations (46.2% vs 10.3%, P = 0.009).

CONCLUSION

Somatic USP8 gene mutations are a common cause of pediatric CD. Patients harboring a somatic mutation had a higher likelihood of tumor recurrence, highlighting the potential importance of this molecular defect for the disease prognosis and the development of targeted therapeutic options.

Association of a PARK2 Germline Variant and Epithelial Ovarian Cancer in a Southern Brazilian Population

Ovarian cancer (OC) is the eighth most common cancer among women in Brazil and seventh in the world population. OC has a high mortality rate and is difficult to diagnose. Currently, OC detection most often occurs at an advanced stage of the disease due to its silent progression, which contributes to the high mortality rate. Available genetic markers are not considered specifically enough for an initial and definite diagnosis. The association with new genes involved with OC can provide a better understanding of this pathology as well as contribute to the development of a marker scenario, providing an improvement in the treatment and survival of patients. The aim of this study was to examine the potential association between the PARK2 gene and epithelial ovarian cancer (EOC). Accordingly, we conducted a study for which 25 patients and 87 controls were recruited. Linkage disequilibrium analysis showed that the four studied tag SNPs (rs2803073, rs6930532, rs1040079, and rs2276201) were independent. Our results using the multivariate analysis between the additive and dominant model demonstrated that tag SNP rs2803073 of PARK2 is associated with susceptibility to EOC (p = 0.018, OR = 0.42). These findings suggest that hereditary variation in the PARK2 gene could influence EOC development mechanisms.

Central precocious puberty in a girl and early puberty in her brother caused by a novel mutation in the MKRN3 gene

CONTEXT

Central precocious puberty (CPP), defined as the development of secondary sex characteristics prior to age 8 years in girls and 9 years in boys, results from the premature activation of the hypothalamic-pituitary-gonadal axis. Mutations in the imprinted gene MKRN3 have been recently implicated in familial cases of CPP.

OBJECTIVE

The objective of the study was to uncover the genetic cause of CPP in a family with two affected siblings.

DESIGN AND PARTICIPANTS

The entire coding region of the paternally expressed MKRN3 gene was sequenced in two siblings, a girl with CPP and her brother with early puberty, their parents, and their grandparents.

RESULTS

A novel heterozygous missense variant in the MKRN3 gene (p.C340G) was detected in the two affected siblings, their unaffected father, and the paternal grandmother. As expected, the mutated allele followed an imprinted mode of inheritance within the affected family. In silico analysis predicts the mutation as possibly damaging in all five software packages used. Furthermore, structural alignment of the ab initio native and mutant MKRN3 models predicts that the p.C340G mutation leads to significant structural perturbations in the 3-dimensional structure of the C3HC4 really interesting new gene motif of the protein, further emphasizing the functional implications of the novel MKRN3 alteration.

CONCLUSIONS

We report a novel MKRN3 mutation (p.C340G) in a girl with CPP and her brother with early puberty. MKRN3 alterations should be suspected in all cases with familial CPP or early puberty, especially if male patients are also involved or the precocious puberty trend does not follow the usually observed mother-to-daughter inheritance.

CYP21A2 mutations in women with polycystic ovary syndrome (PCOS)

The question of the contribution of CYP21A2 heterozygosity to the development of polycystic ovary syndrome (PCOS) has repeatedly been raised in the literature. The available data, however, do not offer a satisfactory answer. The discrepancy must be attributed, primarily, to the small number of subjects in the various studies, the type of selected phenotype, and the number of searched mutations. The aim of the study was to define the contribution of CYP21A2 heterozygous mutations to the pathogenesis of PCOS. We searched for 14 molecular defects of the CYP21A2 gene in 197 PCOS women, employing allele specific PCR. Androgen levels were determined at baseline by appropriate methodology in the follicular phase. PCOS women with 17-hydroxyprogesterone (17OHP) basal values >2 ng/ml and/or post-ACTH >10 ng/ml were excluded. Appropriate controls were included. The frequency of the CYP21A2 heterozygous mutations in PCOS women and in controls was 7.6% and 5.9%, respectively [p-value (PCOS vs. controls): 0.663]. Homozygosity for CYP21A2 gene defects was not detected. In conclusion, the contribution of CYP21A2 heterozygous mutations to the pathogenesis of PCOS is not substantiated by our data. Moreover, 17-hydroxyprogesterone values of < 10 ng/ml post-ACTH exclude homozygosity of CYP21A2 mutations.