Novel variants ensued genomic imprinting in familial central precocious puberty

INTRODUCTION

Central precocious puberty (CPP) is characterized by the early onset of puberty and is associated with the critical processes involved in the pubertal switch. The puberty-related gene pool in the human genome is considerably large though few have been described in CPP. Within those genes, the genomic imprinting features of the MKRN3 and DLK1 genes add additional complexity to the understanding of the pathologic pathways. This study aimed to investigate the molecular etiology in the CPP cohort.

METHODS

Eighteen familial CPP cases were investigated by Sanger sequencing for five CPP-related genes; DLK1, KISS1, KISS1R, MKRN3, and PROKR2. Segregation analysis was performed in all patients with pathogenic variants. Using an ELISA test, the functional pathogenicity of novel variants was also investigated in conjunction with serum delta-like 1 homolog (DLK1) concentrations.

RESULTS

In three probands, a known variant in the MKRN3 gene (c.982C>T/p.(Arg328Cys)) and two novel variants in the DLK1 gene (c.357C>G/p.(Tyr119Ter) and c.67+78C>T) were identified. All three were inherited from the paternal allele. The individuals carrying the DLK1 variants had low detectable DLK1 levels in their serum.

CONCLUSIONS

The frequencies were 5.5% (1/18) for MKRN3 11% (2/18) for DLK1, and none for either KISS1, KISS1R, and PROKR2. Low serum DLK1 levels in affected individuals supported the relationship between here described novel DLK1 gene variants with CPP. Nonsense nature of c.357C>G/p.(Tyr119Ter) and an alteration in the evolutionarily conserved nucleotide c.67+78C>T suggested the disruptive nature of the variant's compatibility with CPP.

SLC34A3 GENE MUTATION AS A RARE CAUSE OF HYPOPHOSPHATEMIA IN TWO SIBLINGS

Context

Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare autosomal recessive disorder, which is characterized by renal phosphate wasting, hypercalciuria, increased 1,25-dihydroxyvitamin D, and decreased parathormone (PTH) levels.

Objective

Here we report different clinical features of two siblings with HHRH, confirmed with molecular diagnosis.

Subjects and methods

16.4 years old boy (P1), and 8.7 years old girl (P2) were referred to our outpatient clinic due to clinical suspicion of metabolic bone diseases.

Results

P1 had severe hypophosphatemia. Additionally, PTH concentration was near to the lower limit, 1,25-dihydroxyvitamin-D concentration was near to the upper limit. P2 had relatively milder clinical and laboratory findings. Bilateral renal calculi were detected on ultrasound in both of them. HHRH was suspected due to their described biochemistry and the presence of bilateral renal calculi. Molecular analysis of SLC34A3 gene revealed a homozygous variant c.756G>A (p.Gln252=) and a splice donor variant c.1335+2T>A. After oral phosphate treatment, clinical and biochemical improvements were observed. However treatment nonadherence of patients was a barrier to reach treatment goal.

Conclusion

The clinical phenotype due to the same mutation in the SLC34A3 gene may vary even among the members of the same family. An accurate diagnosis is important for the appropriate treatment.

Heart and Aorta Anomalies in Turner Syndrome and Relation with Karyotype

Objectives

Turner Syndrome (TS) is associated with a high risk of cardiac anomalies and cardiovascular disease. We aimed to evaluate patients with TS (n=33) for cardiac and aortic pathology using thorax magnetic resonance angiography (MRA).

Subjects and methods

Clinical findings, karyotypes, echocardiogram (ECHO) findings and thorax MRA results were evaluated. Aortic dimensions were measured and standard Z scores of aortic diameters along with aortic size index (ASI) were calculated.

Results

Mean age of the patients was 13.7±3.4 years. MRA revealed cardiovascular pathology in 10 patients (30%). CoA (n=4), aberrant right subclavian artery (n=3), dilatation of the ascending aorta (n=1), tortuosity of the descending aorta (n=1) and fusiform dilatation of the left subclavian artery (n=1) were found. Two of the four patients with CoA found on MRA were detected with ECHO. Mean diameter of the sinotubular junction was found to be elevated [mean±SD: 2.4±1.5]. Z scores for the diameters of the isthmus, ascending aorta and descending aorta were in normal ranges. 45,X patients were found to have significantly higher ASI values than non 45,X patients (p=0.036).

Conclusion

Our findings indicate that patients with TS should be evaluated with MR imaging studies in addition to ECHO to reveal additional subtle cardiac and vascular anomalies. CoA which is very distally located or which has mild nature may not be seen by ECHO. The increase in ASI observed in 45,X patients may herald the development of life-threatening complications. Therefore, frequent follow-up is warranted in these patients.