Single-Exon Deletions of ZNRF3 Exon 2 Cause Congenital Adrenal Hypoplasia

CONTEXT

Primary adrenal insufficiency (PAI) is a life-threatening condition characterized by the inability of the adrenal cortex to produce sufficient steroid hormones. E3 ubiquitin protein ligase zinc and ring finger 3 (ZNRF3) is a negative regulator of Wnt/β-catenin signaling. R-spondin 1 (RSPO1) enhances Wnt/β-catenin signaling via binding and removal of ZNRF3 from the cell surface.

OBJECTIVE

This work aimed to explore a novel genetic form of PAI.

METHODS

We analyzed 9 patients with childhood-onset PAI of biochemically and genetically unknown etiology using array comparative genomic hybridization. To examine the functionality of the identified single-exon deletions of ZNRF3 exon 2, we performed three-dimensional (3D) structure modeling and in vitro functional studies.

RESULTS

We identified various-sized single-exon deletions encompassing ZNRF3 exon 2 in 3 patients who showed neonatal-onset adrenal hypoplasia with glucocorticoid and mineralocorticoid deficiencies. Reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed that the 3 distinct single-exon deletions were commonly transcribed into a 126-nucleotide deleted mRNA and translated into 42-amino acid deleted protein (ΔEx2-ZNRF3). Based on 3D structure modeling, we predicted that interaction between ZNRF3 and RSPO1 would be disturbed in ΔEx2-ZNRF3, suggesting loss of RSPO1-dependent activation of Wnt/β-catenin signaling. Cell-based functional assays with the TCF-LEF reporter showed that RSPO1-dependent activation of Wnt/β-catenin signaling was attenuated in cells expressing ΔEx2-ZNRF3 as compared with those expressing wild-type ZNRF3.

CONCLUSION

We provided genetic evidence linking deletions encompassing ZNRF3 exon 2 and congenital adrenal hypoplasia, which might be related to constitutive inactivation of Wnt/β-catenin signaling by ΔEx2-ZNRF3.

Clinical usefulness of multigene screening with phenotype-driven bioinformatics analysis for the diagnosis of patients with monogenic diabetes or severe insulin resistance

AIMS

Monogenic diabetes is clinically heterogeneous and differs from common forms of diabetes (type 1 and 2). We aimed to investigate the clinical usefulness of a comprehensive genetic testing system, comprised of targeted next-generation sequencing (NGS) with phenotype-driven bioinformatics analysis in patients with monogenic diabetes, which uses patient genotypic and phenotypic data to prioritize potentially causal variants.

METHODS

We performed targeted NGS of 383 genes associated with monogenic diabetes or common forms of diabetes in 13 Japanese patients with suspected (n = 10) or previously diagnosed (n = 3) monogenic diabetes or severe insulin resistance. We performed in silico structural analysis and phenotype-driven bioinformatics analysis of candidate variants from NGS data.

RESULTS

Among the patients suspected having monogenic diabetes or insulin resistance, we diagnosed 3 patients as subtypes of monogenic diabetes due to disease-associated variants of INSR, LMNA, and HNF1B. Additionally, in 3 other patients, we detected rare variants with potential phenotypic effects. Notably, we identified a novel missense variant in TBC1D4 and an MC4R variant, which together may cause a mixed phenotype of severe insulin resistance.

CONCLUSIONS

This comprehensive approach could assist in the early diagnosis of patients with monogenic diabetes and facilitate the provision of tailored therapy.

Pregnancy outcome of Japanese patients with glucokinase-maturity-onset diabetes of the young

AIMS/INTRODUCTION

Glucokinase-maturity-onset diabetes of the young (GCK-MODY; also known as MODY2) is a benign hyperglycemic condition, which generally does not require medical interventions. The only known exception is increased birthweight and related perinatal complications in unaffected offspring of affected women. As previous data were obtained mostly from white Europeans, the present study analyzed the pregnancy outcomes of Japanese women with GCK-MODY to better formulate the management plan for this population.

MATERIALS AND METHODS

The study participants were 34 GCK-MODY families whose members were diagnosed at Osaka City General Hospital during 2010-2017. A total of 53 pregnancies (40 from 23 affected women, 13 from 11 unaffected women) were retrospectively analyzed by chart review.

RESULTS

Birthweights of unaffected offspring born to affected women were significantly greater as compared with those of affected offspring (P = 0.003). The risk of >4,000 g birthweight (16%), however, was lower as compared with that previously reported for white Europeans, and none of the offspring had complications related to large birthweight. Insulin treatment of the affected women resulted in a significant reduction in the birthweights of unaffected offspring. Perinatal complications including small-for-gestational age birthweight were found only in affected offspring born to insulin-treated women.

CONCLUSIONS

In Japanese GCK-MODY families, unaffected offspring born to affected women were heavier than affected offspring. However, insulin treatment of affected women might not be advisable because of the lower risk of macrosomic birth injury, and an increased risk of perinatal complications in affected offspring.

Structural Basis and Genotype-Phenotype Correlations of INSR Mutations Causing Severe Insulin Resistance

The insulin receptor (INSR) gene was analyzed in four patients with severe insulin resistance, revealing five novel mutations and a deletion that removed exon 2. A patient with Donohue syndrome (DS) had a novel p.V657F mutation in the second fibronectin type III domain (FnIII-2), which contains the α-β cleavage site and part of the insulin-binding site. The mutant INSR was expressed in Chinese hamster ovary cells, revealing that it reduced insulin proreceptor processing and impaired activation of downstream signaling cascades. Using online databases, we analyzed 82 INSR missense mutations and demonstrated that mutations causing DS were more frequently located in the FnIII domains than those causing the milder type A insulin resistance (P = 0.016). In silico structural analysis revealed that missense mutations predicted to severely impair hydrophobic core formation and stability of the FnIII domains all caused DS, whereas those predicted to produce localized destabilization and to not affect folding of the FnIII domains all caused the less severe Rabson-Mendenhall syndrome. These results suggest the importance of the FnIII domains, provide insight into the molecular mechanism of severe insulin resistance, will aid early diagnosis, and will provide potential novel targets for treating extreme insulin resistance.

Molecular and clinical characterization of glucokinase maturity-onset diabetes of the young (GCK-MODY) in Japanese patients

AIMS

To investigate the molecular and clinical characteristics of the largest series of Japanese patients with glucokinase maturity-onset diabetes of the young (GCK-MODY), and to find any features specific to Asian people.

METHODS

We enrolled 78 Japanese patients with GCK-MODY from 41 families (55 probands diagnosed at the age of 0-14 years and their 23 adult family members). Mutations were identified by direct sequencing or multiplex ligation-dependent probe amplification of all exons of the GCK gene. Detailed clinical and laboratory data were collected on the probands using questionnaires, which were sent to the treating physicians.　Data on current clinical status and HbA1c levels were also collected from adult patients.

RESULTS

A total of 35 different mutations were identified, of which seven were novel. Fasting blood glucose and HbA1c levels of the probands were ≤9.3 mmol/l and ≤56 mmol/mol (7.3%), respectively, and there was considerable variation in their BMI percentiles (0.4-96.2). In total, 25% of the probands had elevated homeostatic assessment of insulin resistance values, and 58.3% of these had evidence of concomitant Type 2 diabetes in their family. The HbA1c levels for adults were slightly higher, up to 61 mmol/mol (7.8%). The incidence of microvascular complications was low. Out of these 78 people with GCK-MODY and 40 additional family members with hyperglycaemia whose genetic status was unknown, only one had diabetic nephropathy.

CONCLUSIONS

The molecular and clinical features of GCK-MODY in Japanese people are similar to those of other ethnic populations; however, making a diagnosis of GCK-MODY was more challenging in patients with signs of insulin resistance.

Efficacy and safety of long-term, continuous subcutaneous octreotide infusion for patients with different subtypes of KATP-channel hyperinsulinism

OBJECTIVE

To evaluate the efficacy of long-term, continuous, subcutaneous octreotide infusion for congenital hyperinsulinism caused by mutations in the KATP-channel genes, KCNJ11 and ABCC8.

PATIENTS

Fifteen Japanese patients with diazoxide-unresponsive, KATP-channel hyperinsulinism.

METHODS

Molecular diagnoses were made by sequencing and multiple ligation-dependent probe amplification analysis. In patients with paternally inherited, monoallelic mutations, 18F-DOPA PET scans were performed to determine the location of the lesion. The patients were treated with continuous, subcutaneous octreotide infusion at a dosage of up to 25 μg/kg/day, using an insulin pump to maintain blood glucose levels higher than 3.33 mmol/l. Additional treatments (IV glucose, glucagon or enteral feeding) were administered as needed. The efficacy of the treatment was assessed in patients who received octreotide for 4 months to 5.9 years.

RESULTS

Three patients had biallelic mutations, and 12 had monoallelic, paternally inherited mutations. Four patients with monoallelic mutations showed diffuse 18F-DOPA uptake, whereas seven patients showed focal uptake. Octreotide was effective in all the patients. The patients with biallelic mutations required a higher dosage (17-25 μg/kg/day), and two patients required additional treatments. By contrast, the patients with monoallelic mutations required a lower dosage (0.5-21 μg/kg/day) irrespective of the PET results and mostly without additional treatments. Treatment was discontinued in three patients at 2.5, 3.3 and 5.9 years of age, without psychomotor delay. Except for growth deceleration at a higher dosage, no significant adverse effects were noted.

CONCLUSIONS

Long-term, continuous, subcutaneous octreotide infusion is a feasible alternative to surgery especially for patients with monoallelic KATP-channel mutations.

Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

BACKGROUND

In Asians, mutations in the known maturity-onset diabetes of the young (MODY) genes have been identified in only <15% of patients. These results were obtained mostly through studies on adult patients.

OBJECTIVE

To investigate the molecular basis of Japanese patients with pediatric-onset MODY-type diabetes.

SUBJECTS

Eighty Japanese patients with pediatric-onset MODY-type diabetes.

METHODS

Mitochondrial 3243A>G mutation was first tested by the polymerase chain reaction restriction fragment length polymorphism analysis for maternally inherited families. Then, all coding exons and exon-intron boundaries of the HNF1A, HNF1B, GCK, and HNF4A genes were amplified from genomic DNA and directly sequenced. Multiplex ligation-dependent probe amplification analysis was also performed to detect whole-exon deletions.

RESULTS

After excluding one patient with a mitochondrial 3243A>G, mutations were identified in 38 (48.1%) patients; 18 had GCK mutations, 11 had HNF1A mutations, 3 had HNF4A mutations, and 6 had HNF1B mutations. In patients aged <8 yr, mutations were detected mostly in GCK at a higher frequency (63.6%). In patients >9 yr of age, mutations were identified less frequently (45.1%), with HNF1A mutations being the most frequent. A large fraction of mutation-negative patients showed elevated homeostasis model assessment (HOMA) insulin-resistance and normal HOMA-β indices. Most of the HNF1B mutations were large deletions, and, interestingly, renal cysts were undetectable in two patients with whole-gene deletion of HNF1B.

CONCLUSION

In Japanese patients with pediatric-onset MODY-type diabetes, mutations in known genes were identified at a much higher frequency than previously reported for adult Asians. A fraction of mutation-negative patients presented with insulin-resistance and normal insulin-secretory capacities resembling early-onset type 2 diabetes.

Significance of Helicobacter pylori infection as a risk factor in gastric cancer: serological and histological studies

We conducted a case-control study to examine the association of Helicobacter pylori infection as a risk factor in gastric cancer in the Japanese population. Serum IgG antibodies for Helicobacter pylori were determined in 55 consecutive patients with gastric cancer and in 75 age- and sex-matched mass survey subjects and 57 age- and sex-matched cancer-free patients with conditions considered at a high risk for development of gastric cancer (precancerous condition). We examined the histology in all subjects and particular focus was placed on the extent of Helicobacter pylori-associated gastritis. The seroprevalence of Helicobacter pylori in gastric cancer patients (82%) and those with a precancerous condition (89%) was significantly higher (P < 0.005) than that in the mass survey subjects (60%). Positive relative risk associations were found for patients with gastric cancer (odds ratio, 3, with 95% confidence intervals of 1.69-5.33) and those with a precancerous condition (odds ratio, 5.66, with 95% confidence intervals 2.66-12.03). Significant differences were found when comparisons were made among the case-control groups who were H. pylori-positive and had inflammatory cell infiltration (P = 0.0127). The characteristics of Helicobacter pylori in histologically examined gastric mucosa showed differences between Helicobacter pylori-infected and uninfected persons in all groups. However, for none of these groups was there a significant differences between background mucosa for Helicobacter pylori-infected persons with or without gastric cancer. Helicobacter pylori seroprevalence is strongly associated with an increased risk of gastric cancer and with a precancerous condition; histological investigation did not define additional factors that might be associated with increased cancer risk.

Refinement of the locus for X-linked recessive chondrodysplasia punctata

Although the locus for X-linked recessive chondrodysplasia punctata (CDPX1) has been mapped to the region between PABX and DXS31 (the critical region is about 3 Mb long), the precise location within the critical region has not been determined. In this paper, we describe a boy with a 46,Y,der(X)t(X;Y)(p22.3;q11)mat karyotype and review the genotype-phenotype correlations in three male patients with the combination of apparent lack of clinical features of CDPX1 and a partial deletion of the critical region. The results suggest that the region defined by the two BssHII sites at 3180 and 3570 kb from the Xp telomere may be the target region for the CDPX1 locus.