Looking for the hidden mutation: Bannayan-Riley-Ruvalcaba syndrome caused by constitutional and mosaic 10q23 microdeletions involving PTEN and BMPR1A.

The PTEN hamartoma tumor syndrome (PHTS) is caused by heterozygous germline variants in PTEN. Here, we report two unrelated patients with juvenile polyposis, macrocephaly, intellectual disability, and hyperpigmented skin macules. Both patients were clinically suspected for the Bannayan-Riley-Ruvalcaba syndrome (BRRS), a PHTS subentity. By array-CGH analysis, we identified an interstitial 10q23.1q23.3 deletion in a buccal mucosa sample of Patient 1 that encompassed PTEN, BMPR1A, and KLLN, among others. In contrast, neither sequencing nor array-CGH analysis identified a pathogenic variant in PTEN or BMPR1A in a blood sample of Patient 2. However, in a surgical specimen of the thyroid gland high-level mosaicism for a 10q23.2q23.3 deletion was observed. Additionally, the pathogenic PTEN variant c.956_959delCTTT p.(Thr319LysfsTer24) was detected in his thyroid tissue. The frame shift variant was neither detected in the patient's blood nor in his buccal mucosa sample. Low-level mosaicism for the microdeletion was identified in a buccal swap sample, and reanalysis of the blood sample suggested marginal-level mosaicism for deletion. The 10q23.2q23.3 deletion mosaicism was also identified in a subsequently resected colonic polyp. Thus, in both cases, the diagnosis of a 10q23 deletion syndrome, which clinically presented as BRRS, was established. Overall, the study expands the BRRS spectrum and highlights the relevance of considering mosaicism in PHTS. We conclude that in all patients with a clear clinical suspicion of PHTS, in which genetic analyses of DNA from blood and buccal swap samples fail to identify causative genetic variants, genetic analyses of additional tissues are recommended.

The A645D mutation in the hinge region of the human androgen receptor (AR) gene modulates AR activity, depending on the context of the polymorphic glutamine and glycine repeats.

BACKGROUND: Sufficient androgen receptor (AR) activity is crucial for normal male sexual differentiation. Here we report on two unrelated 46, XY patients suffering from undervirilization and genital malformations. Both patients had a short polyglycine (polyG) repeat of 10 residues and a relatively long polyglutamine (polyQ) repeat of 28 and 30 residues within the transactivation domain of the AR. In addition, they also harbor a rare A645D substitution. OBJECTIVE: We made a set of AR expression plasmid constructs with varying polyQ and polyG tract sizes in context with or without the A645D substitution and analyzed their in vitro transactivation capacity in transfected CHO cells. RESULTS: We found that a short polyG repeat downmodulated AR activity to approximately 60-65% of the wild-type receptor. This effect was aggravated by A645D in context of a long polyQ repeat to less than 50% activity. In contrast, in the context of a short polyQ and a short polyG repeat, the A645D mutation rescues AR activity to almost wild-type levels, demonstrating a contradictory effect of this mutation, depending on the size of the polymorphic repeats. CONCLUSIONS: A combination of a short polyG repeat with a long polyQ repeat and an A645D substitution might contribute to the development of virilization disorders and explain the observed phenotypes of our patients as a form of androgen insensitivity. The whole recreation of AR sequence variations including individual polymorphic repeat sizes could unravel possible interference of mutations and variations on AR activity by in vitro transfection.

Thirteen novel mutations in the NR0B1 (DAX1) gene as cause of adrenal hypoplasia congenita.

X-linked adrenal hypoplasia congenita (AHC) is a rare developmental disorder associated with primary adrenal insufficiency and combined primary and secondary male hypogonadism. It is caused by deletions or mutations of the NR0B1 (DAX1) gene encoding DAX1, an atypical orphan member of the nuclear receptor superfamily. The continuous molecular genetic analysis of male patients with primary adrenal insufficiency revealed 13 novel mutations within the coding region of the NR0B1 gene which are predicted to inactivate the DAX1 function. These were three nonsense mutations (c.312C>A, p.Cys104X, c.670C>T, p.Gln224X; and c.873G>A, p.Trp291X), five duplications (c.269_270dup, c.421_422dup, c.895_896dup, c.989dup, c.999_1000dup), and five deletions (c.483del, c.745_746del, c.734_740del, c.1092del, and c.1346del). All of the mutations resulted in a premature stop codon destroying the ligand binding domain of the predictive DAX1 protein.

Autosomal-dominant pseudohypoaldosteronism type 1 in a Turkish family is associated with a novel nonsense mutation in the human mineralocorticoid receptor gene.

Pseudohypoaldosteronism type 1 (PHA1) is a rare congenital disease inherited in either an autosomal-recessive or an autosomal-dominant trait. The autosomal-dominant form manifests with renal salt loss in infancy and a gradual improvement with advancing age. PHA1 presents with potential life-threatening salt wasting and failure to thrive in early infancy. Autosomal-dominant forms of PHA1 are often caused by heterozygous mutations of the MR gene coding for the mineralocorticoid receptor. Whether heterozygous mutations of the MR gene impair biological function as a result of haplo-insufficiency or due to a dominant-negative effect needs further clarification. We report a case of a renal form of PHA1 in a Turkish family. A heterozygous nonsense mutation c3055C>T (R947X) in exon 9 of the MR gene leading to a premature stop codon was identified in the index patient. The truncated receptor is free of aldosterone binding. The segregation analysis revealed the identical mutation in the patient's father, who never showed any symptoms of PHA. This shows the incomplete penetrance of the phenotype, although a mild salt loss might have been overlooked in the father's childhood.

Identification of a novel mutation in the human mineralocorticoid receptor gene in a german family with autosomal-dominant pseudohypoaldosteronism type 1: further evidence for marked interindividual clinical heterogeneity.

Pseudohypoaldosteronism (PHA) type 1 presents in infancy with potential life-threatening salt wasting and failure to thrive. Plasma renin activity and aldosterone levels are markedly elevated. PHA1 is inherited in either an autosomal recessive or autosomal dominant trait. The autosomal dominant form manifests with renal salt loss in infancy and a gradual improvement with advancing age. We report the case of a renal form of PHA1 in a German family. PCR and direct sequencing revealed a heterozygous point mutation, c488C>G (S163X), leading to a premature stop codon in the index patient. The segregation analysis revealed the identical mutation in the patient's father, who showed no symptoms of PHA at the time of investigation or before. The family was screened for amino acid polymorphisms in the amiloride-sensitive epithelial sodium channel, which could be a cause for phenotypic differences within the family. PCR and direct sequencing revealed identical epithelial sodium channel haplotypes in the patient and his father. These polymorphisms can, therefore, not be responsible for the difference in clinical presentation. It remains to be elucidated whether other defects or polymorphisms in genes coding for regulatory proteins participating in sodium homeostasis are a cause of the heterogeneity of the clinical manifestations in autosomal dominant PHA1.