Genetic testing of children with familial tall stature: is it worth doing?

CONTEXT

Familial tall stature (FTS) is considered to be a benign variant of growth with a presumed polygenic etiology. However, monogenic disorders with possible associated pathological features could also be hidden under the FTS phenotype.

OBJECTIVES

To elucidate the genetic etiology in families with FTS and to describe their phenotype in detail.

DESIGN, SETTINGS AND PATIENTS

Children with FTS (height in both the child and his/her taller parent >2 SD) referred to the Endocrinology center of Motol University Hospital were enrolled to the study. Their DNA was examined cytogenetically and via next-generation sequencing panel of 786 genes associated with growth. The genetic results were evaluated by the American College of Molecular Genetics and Genomics guidelines. All of the participants underwent standard endocrinological examination followed by specialized anthropometric evaluation.

RESULTS

In total, 34 children (19 girls) with FTS were enrolled in the study. Their median height and their taller parent's height were 3.1 SD and 2.5 SD, respectively. The genetic cause of FTS was elucidated in 11/34 (32.4%) children (47, XXX and 47, XYY karyotypes, SHOX duplication, and causative variants in NSD1 [in 2], SUZ12 [in 2], FGFR3, CHD8, GPC3, and PPP2R5D genes). Ten children had absent syndromic sings and 24 had dysmorphic features.

CONCLUSION

Monogenic (and cytogenetic) etiology of FTS can be found among children with FTS. Genetic examination should be considered in all children with FTS regardless of the presence of dysmorphic features.

Paediatric diabetes subtypes in a consanguineous population: a single-centre cohort study from Kurdistan, Iraq

AIMS/HYPOTHESIS

Monogenic diabetes is estimated to account for 1-6% of paediatric diabetes cases in primarily non-consanguineous populations, while the incidence and genetic spectrum in consanguineous regions are insufficiently defined. In this single-centre study we aimed to evaluate diabetes subtypes, obtain the consanguinity rate and study the genetic background of individuals with syndromic and neonatal diabetes in a population with a high rate of consanguinity.

METHODS

Data collection was carried out cross-sectionally in November 2021 at the paediatric diabetic clinic, Dr Jamal Ahmad Rashed Hospital, in Sulaimani, Kurdistan, Iraq. At the time of data collection, 754 individuals with diabetes (381 boys) aged up to 16 years were registered. Relevant participant data was obtained from patient files. Consanguinity status was known in 735 (97.5%) participants. Furthermore, 12 families of children with neonatal diabetes and seven families of children with syndromic diabetes consented to genetic testing by next-generation sequencing. Prioritised variants were evaluated using the American College of Medical Genetics and Genomics guidelines and confirmed by Sanger sequencing.

RESULTS

A total of 269 of 735 participants (36.5%) with known consanguinity status were offspring of consanguineous families. An overwhelming majority of participants (714/754, 94.7%) had clinically defined type 1 diabetes (35% of them were born to consanguineous parents), whereas only eight (1.1%) had type 2 diabetes (38% consanguineous). Fourteen (1.9%) had neonatal diabetes (50% consanguineous), seven (0.9%) had syndromic diabetes (100% consanguineous) and 11 (1.5%) had clinically defined MODY (18% consanguineous). We found that consanguinity was significantly associated with syndromic diabetes (p=0.0023) but not with any other diabetes subtype. The genetic cause was elucidated in ten of 12 participants with neonatal diabetes who consented to genetic testing (homozygous variants in GLIS3 [sibling pair], PTF1A and ZNF808 and heterozygous variants in ABCC8 and INS) and four of seven participants with syndromic diabetes (homozygous variants in INSR, SLC29A3 and WFS1 [sibling pair]). In addition, a participant referred as syndromic diabetes was diagnosed with mucolipidosis gamma and probably has type 2 diabetes.

CONCLUSIONS/INTERPRETATION

This unique single-centre study confirms that, even in a highly consanguineous population, clinically defined type 1 diabetes is the prevailing paediatric diabetes subtype. Furthermore, a pathogenic cause of monogenic diabetes was identified in 83% of tested participants with neonatal diabetes and 57% of participants with syndromic diabetes, with most variants being homozygous. Causative genes in our consanguineous participants were markedly different from genes reported from non-consanguineous populations and also from those reported in other consanguineous populations. To correctly diagnose syndromic diabetes in consanguineous populations, it may be necessary to re-evaluate diagnostic criteria and include additional phenotypic features such as short stature and hepatosplenomegaly.

Analysis of children with familial short stature: who should be indicated for genetic testing?

Familial short stature (FSS) describes vertically transmitted growth disorders. Traditionally, polygenic inheritance is presumed, but monogenic inheritance seems to occur more frequently than expected. Clinical predictors of monogenic FSS have not been elucidated. The aim of the study was to identify the monogenic etiology and its clinical predictors in FSS children. Of 747 patients treated with growth hormone (GH) in our center, 95 with FSS met the inclusion criteria (pretreatment height ≤-2 SD in child and his/her shorter parent); secondary short stature and Turner/Prader-Willi syndrome were excluded criteria. Genetic etiology was known in 11/95 children before the study, remaining 84 were examined by next-generation sequencing. The results were evaluated by American College of Medical Genetics and Genomics (ACMG) guidelines. Nonparametric tests evaluated differences between monogenic and non-monogenic FSS, an ROC curve estimated quantitative cutoffs for the predictors. Monogenic FSS was confirmed in 36/95 (38%) children. Of these, 29 (81%) carried a causative genetic variant affecting the growth plate, 4 (11%) a variant affecting GH-insulin-like growth factor 1 (IGF1) axis and 3 (8%) a variant in miscellaneous genes. Lower shorter parent's height (P = 0.015) and less delayed bone age (BA) before GH treatment (P = 0.026) predicted monogenic FSS. In children with BA delayed less than 0.4 years and with shorter parent's heights ≤-2.4 SD, monogenic FSS was revealed in 13/16 (81%) cases. To conclude, in FSS children treated with GH, a monogenic etiology is frequent, and gene variants affecting the growth plate are the most common. Shorter parent's height and BA are clinical predictors of monogenic FSS.

The Genetic Landscape of Children Born Small for Gestational Age with Persistent Short Stature

INTRODUCTION

Among children born small for gestational age, 10-15% fail to catch up and remain short (SGA-SS). The underlying mechanisms are mostly unknown. We aimed to decipher genetic aetiologies of SGA-SS within a large single-centre cohort.

METHODS

Out of 820 patients treated with growth hormone (GH), 256 were classified as SGA-SS (birth length and/or birth weight <-2 SD for gestational age and life-minimum height <-2.5 SD). Those with the DNA triplet available (child and both parents) were included in the study (176/256). Targeted testing (karyotype/FISH/MLPA/specific Sanger sequencing) was performed if a specific genetic disorder was clinically suggestive. All remaining patients underwent MS-MLPA to identify Silver-Russell syndrome, and those with unknown genetic aetiology were subsequently examined using whole-exome sequencing or targeted panel of 398 growth-related genes. Genetic variants were classified using ACMG guidelines.

RESULTS

The genetic aetiology was elucidated in 74/176 (42%) children. Of these, 12/74 (16%) had pathogenic or likely pathogenic (P/LP) gene variants affecting pituitary development (LHX4, OTX2, PROKR2, PTCH1, POU1F1), the GH-IGF-1 or IGF-2 axis (GHSR, IGFALS, IGF1R, STAT3, HMGA2), 2/74 (3%) the thyroid axis (TRHR, THRA), 17/74 (23%) the cartilaginous matrix (ACAN, various collagens, FLNB, MATN3), and 7/74 (9%) the paracrine chondrocyte regulation (FGFR3, FGFR2, NPR2). In 12/74 (16%), we revealed P/LP affecting fundamental intracellular/intranuclear processes (CDC42, KMT2D, LMNA, NSD1, PTPN11, SRCAP, SON, SOS1, SOX9, TLK2). SHOX deficiency was found in 7/74 (9%), Silver-Russell syndrome in 12/74 (16%) (11p15, UPD7), and miscellaneous chromosomal aberrations in 5/74 (7%) children.

CONCLUSIONS

The high diagnostic yield sheds a new light on the genetic landscape of SGA-SS, with a central role for the growth plate with substantial contributions from the GH-IGF-1 and thyroid axes and intracellular regulation and signalling.

Search for a time- and cost-saving genetic testing strategy for maturity-onset diabetes of the young

AIMS

Correct genetic diagnosis of maturity-onset diabetes of the young (MODY) is beneficial for person's diabetes management compared to no genetic testing. Aim of the present study was a search for optimal time- and cost-saving strategies by comparing two approaches of genetic testing of participants with clinical suspicion of MODY.

METHODS

A total of 121 consecutive probands referred for suspicion of MODY (Group A) were screened using targeted NGS (tNGS), while the other 112 consecutive probands (Group B) underwent a single gene test based on phenotype, and in cases of negative findings, tNGS was conducted. The study was performed in two subsequent years. The genetic results, time until reporting of the final results and financial expenses were compared between the groups.

RESULTS

MODY was confirmed in 30.6% and 40.2% probands from Groups A and B, respectively; GCK-MODY was predominant (72.2% in Group A and 77.8% in Group B). The median number of days until results reporting was 184 days (IQR 122-258) in Group A and 91 days (44-174) in Group B (p < 0.00001). Mean costs per person were higher for Group A (639 ± 30 USD) than for Group B (584 ± 296 USD; p = 0.044).

CONCLUSIONS

The two-step approach represented a better strategy for genetic investigation of MODY concerning time and costs compared to direct tNGS. Although a single-gene investigation clarified the diabetes aetiology in the majority of cases, tNGS could reveal rare causes of MODY and expose possible limitations of both standard genetic techniques and clinical evaluation.

Invaluable Role of Consanguinity in Providing Insight into Paediatric Endocrine Conditions: Lessons Learnt from Congenital Hyperinsulinism, Monogenic Diabetes, and Short Stature

Consanguineous families have often played a role in the discovery of novel genes, especially in paediatric endocrinology. At this time, it has been estimated that over 8.5% of all children worldwide have consanguineous parents. Consanguinity is linked to demographic, cultural, and religious practises and is more common in some areas around the world than others. In children with endocrine conditions from consanguineous families, there is a greater probability that a single-gene condition with autosomal recessive inheritance is causative. From 1966 and the first description of Laron syndrome, through the discovery of the first KATP channel genes ABCC8 and KCNJ11 causing congenital hyperinsulinism (CHI) in the 1990s, to recent discoveries of mutations in YIPF5 as the first cause of monogenic diabetes due to the disruption of the endoplasmic reticulum (ER)-to-Golgi trafficking in the β-cell and increased ER stress; positive genetic findings in children from consanguinity have been important in elucidating novel genes and mechanisms of disease, thereby expanding knowledge into disease pathophysiology. The aim of this narrative review was to shed light on the lessons learned from consanguineous pedigrees with the help of 3 fundamental endocrine conditions that represent an evolving spectrum of pathophysiological complexity - from CHI, a typically single-cell condition, to monogenic diabetes which presents with uniform biochemical parameters (hyperglycaemia and glycosuria), despite varying aetiologies, up to the genetic regulation of human growth - the most complex developmental phenomenon.

Isolated growth hormone deficiency in children with vertically transmitted short stature: What do the genes tell us?

INTRODUCTION

The growth hormone deficiency (GHD) diagnosis is controversial especially due to low specificity of growth hormone (GH) stimulation tests. It is therefore believed that children diagnosed with GHD form a heterogeneous group with growth disorder frequently independent on GH function. No study evaluating the complex etiology of growth failure in children with diagnosed GHD has been performed thus far.

AIMS

To discover genetic etiology of short stature in children with diagnosed GHD from families with short stature.

METHODS

Fifty-two children diagnosed with primary GHD and vertically transmitted short stature (height SDS in the child and his/her shorter parent <-2 SD) were included to our study. The GHD diagnosis was based on growth data suggestive of GHD, absence of substantial disproportionality (sitting height to total height ratio <-2 SD or >+2 SD), IGF-1 levels <0 for age and sex specific SD and peak GH concentration <10 ug/L in two stimulation tests. All children were examined using next-generation sequencing methods, and the genetic variants were subsequently evaluated by American College of Medical Genetics standards and guidelines.

RESULTS

The age of children at enrollment into the study was 11 years (median, IQR 9-14 years), their height prior to GH treatment was -3.0 SD (-3.6 to -2.8 SD), IGF-1 concentration -1.4 SD (-2.0 to -1.1 SD), and maximal stimulated GH 6.3 ug/L (4.8-7.6 ug/L). No child had multiple pituitary hormone deficiency or a midbrain region pathology. Causative variant in a gene that affects growth was discovered in 15/52 (29%) children. Of them, only 2 (13%) had a genetic variant affecting GH secretion or function (GHSR and OTX2). Interestingly, in 10 (67%) children we discovered a primary growth plate disorder (ACAN, COL1A2, COL11A1, COL2A1, EXT2, FGFR3, NF1, NPR2, PTPN11 [2x]), in one (7%) a genetic variant impairing IGF-1 action (IGFALS) and in two (12%) a variant in miscellaneous genes (SALL4, MBTPS2).

CONCLUSIONS

In children with vertically transmitted short stature, genetic results frequently did not correspond with the clinical diagnosis of GH deficiency. These results underline the doubtful reliability of methods standardly used to diagnose GH deficiency.

Familial Short Stature-A Novel Phenotype of Growth Plate Collagenopathies

CONTEXT

Collagens are the most abundant proteins in the human body. In a growth plate, collagen types II, IX, X, and XI are present. Defects in collagen genes cause heterogeneous syndromic disorders frequently associated with short stature. Less is known about oligosymptomatic collagenopathies.

OBJECTIVE

This work aims to evaluate the frequency of collagenopathies in familial short stature (FSS) children and to describe their phenotype, including growth hormone (GH) treatment response.

METHODS

Eighty-seven FSS children (pretreatment height ≤ -2 SD both in the patient and his or her shorter parent) treated with GH were included in the study. Next-generation sequencing was performed to search for variants in the COL2A1, COL9A1, COL9A2, COL9A3, COL10A1, COL11A1, and COL11A2 genes. The results were evaluated using American College of Medical Genetics and Genomics guidelines. The GH treatment response of affected children was retrospectively evaluated.

RESULTS

A likely pathogenic variant in the collagen gene was found in 10 of 87 (11.5%) children. Detailed examination described mild asymmetry with shorter limbs and mild bone dysplasia signs in 2 of 10 and 4 of 10 affected children, respectively. Their growth velocity improved from a median of 5.3 cm/year to 8.7 cm/year after 1 year of treatment. Their height improved from a median of -3.1 SD to -2.6 SD and to -2.2 SD after 1 and 3 years of therapy, respectively. The final height reached by 4 of 10 children differed by -0.67 to +1.0 SD and -0.45 to +0.5 SD compared to their pretreatment height and their affected untreated parent's height, respectively.

CONCLUSION

Oligosymptomatic collagenopathies are a frequent cause of FSS. The short-term response to GH treatment is promising.

Stratifying the Genetic Aetiology in Children Born Small for Gestational Age With Persistent Short Stature (SGA-SS)

Background: Ten percent of children born small for gestational age with a birth weight and/or length of below -2 SD for their gestational age fail to catch-up and remain short during childhood (SGA-SS). The etiology of SGA-SS is heterogeneous: some children have specific phenotypic features that allow targeted genetic testing; in others, elucidating genetic or environmental background is more challenging. Aim: To decipher genetic etiologies among a large single-center cohort of SGA-SS children and to stratify them according to molecular mechanisms leading to pre- and postnatal growth failure. Patients/Methods: In our center 447 children (223 females) fulfilled the criteria of SGA-SS. Of these 182 families agreed to take part and offered the child’s and both parents’ DNA for genetic testing by a panel of 399 growth-related genes, or by Whole Exome Sequencing (WES). The results were processed by a bioinformatic pipeline and detected variants were filtered using variant analysis software. Pathogenic or likely pathogenic variants (according to ACMG standards and guidelines) were confirmed by Sanger sequencing. Results: The genetic etiology was elucidated in 73/182 (40%) children so far. We confirmed (likely) pathogenic gene variants affecting pituitary development and/or the GH-IGF-1 axis in 10/73 (14%) patients (PTCH1, HGMA2 [in two], OTX2, LHX4, GHSR, STAT3, IGFALS, IGF1R [in two]), abnormal components of cartilaginous matrix in 17/73 (23%) (ACAN [in two], FLNB [in three], FBLN5, COL11A1[in four], COL1A2, COL2A1[in five], MATN3), impaired paracrine regulation of chondrocytes in 4/73 (6%) (NPR2 [in three], FGFR3), SHOX gene defects in 12/73 (16%), gene variants affecting other components of intracellular regulation and signaling in 9/73 (12%) (CDC42, KMT2A, KMT2D, NSD1, SRCAP, PRG4, PTPN11, SON, LMNA), Silver-Russell syndrome (11p15 [in seven] or UPD7) in 11/73 (15%), and miscellaneous single-gene or chromosomal conditions (TRPS1, TRHR, RAI1, chromosomal microdeletions and/or translocations) in an additional ten (14%) children. Conclusions: In our study we showed that by using current genetic techniques we were able to elucidate the genetic cause in a significant number of patients born SGA-SS. The genetic etiology spectrum of SGA-SS reflects the complex system of growth regulation, with a significant role of growth plate genes that are causative in 33/73 (45%) cases clarified thus far. Acknowledgements: The study was co-funded by grants AZV NV18-07-00283 and GAUK 408120.

Growth Plate Genes Are Key Regulators of Growth: Lessons Learned From Children of Consanguineous Families From Kurdistan, Iraq

Introduction: The genetic basis of human growth regulation has only been partly elucidated thus far. Therefore, finding causative genes in patients with short stature help in understanding precise pathophysiological mechanisms, establishing genotype-phenotype relationships and optimizing treatment. In order to extend our knowledge about the genes involved in short stature, we studied a unique cohort of consanguineous families with children with short stature from Sulaymani in Kurdistan, Iraq. Patients and Methods: Fifty-five consanguineous families, with children shorter than -2.3SDS at the time of examination (median height -3.3SDS, range -2.3 to -15SDS), who were examined at the endocrine outpatient clinic of the Department of Pediatrics, Sulaymani University College of Medicine between January 2018 and February 2020, were included in the study. In families with more than one child with short stature, the shorter sibling was selected as the proband (median age 8 years, range 1 - 15 years). Three probands were subsequently excluded due to the diagnosis of Turner’s syndrome and Edward’s syndrome Consent was obtained from all families and probands’ DNA was analyzed by Whole Exome Sequencing (WES) methods. The data were processed by a bioinformatic pipeline and detected variants were filtered using variant analysis software. Selected potentially pathogenic variants were confirmed using Sanger sequencing methods and evaluated by the American College of Medical Genetics (ACMG) standards and guidelines. Results: A monogenic cause of short stature, which explained the patient phenotype, was elucidated in 13 of 26 families who were analyzed thus far. Seven families had multiple affected children making a total of 22 patients with a positive genetic diagnosis. Pathogenic or likely pathogenic variants (according to the ACMG standards) were found in genes involved in the GH-IGF-1 axis (GHR), in the extracellular matrix of the growth plate (COL1A2, MMP13, LTBP3, and ADAMTS17), in the regulation of chondrocytes (NPR2 and CTSK), transporter coding genes (SLC34A3), and other genes (PTCH1, GALNS, DNACJ21, ZSWIM6, GNPTG). Among them, there are 9 novel variants and 10 homozygous variants including variants in genes causing syndromic short stature. Unexpectedly, we successfully identified three cases of autosomal dominant short stature (variants in genes NPR2, COL1A2, PTCH1) as well. The remaining probands from 26 families are still being analyzed. Conclusion: With the help of NGS methods, we have successfully elucidated the genetic cause of short stature in nearly 50% of patients who were analyzed thus far. These results further strength the concept that genes affecting the growth plate (chondrocytes and the extracellular matrix) play a crucial role in growth regulation. Acknowledgements: The study was co-funded by grants AZV 18-07-00283 and GAUK 340420.

Familial Short Stature - a Novel Phenotype of Growth Plate Collagenopathies

Backround: Collagens are the most abundant proteins in the human body. In a growth plate, collagen types II, IX, X and XI are present. Defects in collagen genes cause heterogeneous syndromic disorders frequently associated with asymmetric short stature (e.g. Kniest dysplasia, spondyloepiphyseal dysplasia). Less is known about nonsyndromic collagenopathies - data about their frequency and subtle phenotypic signs are sparse, the information about their response to growth hormone (GH) treatment is lacking completely.

Aim: To evaluate the frequency of collagenopathies in familial short stature (FSS) children and to describe their phenotype, including growth hormone (GH) treatment response.

Methods: Out of 522 individuals treated in our center with GH from the indication of primary GH deficiency (GHD) or small for gestational age short stature (SGA-SS), 87 children with FSS fulfilled the inclusion criteria (pre-treatment height ≤-2 SD in both patient/their shorter parent, signed written informed consent) and were enrolled to the study. Next-generation sequencing was performed to search for variants in COL2A1, COL9A1, COL9A2, COL9A3, COL10A1, COL11A1 and COL11A2 genes. The results were evaluated using ACMG guidelines. The phenotype of children with (likely) pathogenic variants was described including the short-term GH treatment response (growth velocity and body-height SDS increase over three years of treatment). For statistical evaluation, parametric tests were used, p-values <0.05 were considered significant.

Results: A (likely) pathogenic variant in one of the collagen genes was found in 10/87 (11.5%) children. Their age was 12.5 years (median, range 6-17 years), their pre-treatment height was -3.1 SD (-2.4 to -4.3 SD). Their birth length (median -2.8 SD; range -0.7 to -4.1 SD) was more severely affected than birth weight (median -2.1 SD; range -1.0 to -2.7 SD). Eight children were treated with GH from SGA-SS indication, the remaining 2 were classified as mild GHD (maximal stimulated GH concentration 8.0 and 9.7 ug/l, normal brain MRI and examination of other pituitary hormones). Detailed anthropometric examination described mild asymmetry with shorter limbs and mild bone dysplasia signs (scoliosis, more pronounced lumbar lordosis, genua valga, limited elbow extension) in 2/10 and 4/10 affected children, respectively. Growth velocity improved from a median of 5.3 cm/year to 8.7 cm/year after one year of treatment (p<0.001, paired-sample T-test), height improved from a median of -3.1 SD to -2.2 SD after three years of therapy (p=0.001, ANOVA repeated measures analysis of variants).

Conclusion: Nonsyndromic collagenopathies are a frequent cause of FSS. The short-term response to GH treatment is promising.

Supported by the Ministry of Health, Czech Republic, grant number NV18- 07-00283 and by the research project of the Grant Agency of Charles University of Prague, GAUK 976718.

Quality of Life and Treatment Satisfaction in Participants with Maturity-Onset Diabetes of the Young: A Comparison to Other Major Forms of Diabetes

AIMS

We investigated the quality of life (QoL), treatment satisfaction and perception of genetic results in participants with Maturity-Onset Diabetes of the Young (MODY) and compared the results with those of subjects with type 1 (T1D) or type 2 (T2D) diabetes.

METHODS

A total of 162 adults with GCK-MODY, 62 with HNF1A-MODY and 29 with HNF4A-MODY answered the questionnaire Audit of Diabetes Dependent Quality of Life, the Diabetes Treatment Satisfaction Questionnaire and non-validated instrument examining the respondent's perception of the genetic results. Data from GCK-MODY patients were compared with 84 participants with T2D and HNF-MODY subjects were compared with 81 participants having T1D.

RESULTS

Higher age (p=0.004), higher haemoglobin A1c (p=0.026) and medication (p=0.019) were associated with lower general QoL in GCK-MODY patients. In HNF-MODY patients, lower general QoL was associated with a longer time since diagnosis (p=0.005), worse haemoglobin bA1c (p=0.006) and insulin treatment (p=0.019). Similar numbers of participants with GCK- and HNF-MODY considered the genetic diagnosis of MODY to be positive, negative and without significance. The patient with GCK-MODY did not differ from those with T2D in terms of their QoL, but they were less satisfied with their treatment (p<0.001). QoL was better in patients with HNF-MODY compared with patients with T1D (p=0.006), and they did not differ in terms of treatment satisfaction.

CONCLUSIONS

QoL was affected in both GCK-MODY and HNF-MODY subjects. Apprehension of genetic diagnosis was not single-valued in MODY respondents.

Functional Analyses of HNF1A-MODY Variants Refine the Interpretation of Identified Sequence Variants

CONTEXT

While rare variants of the hepatocyte nuclear factor-1 alpha (HNF1A) gene can cause maturity-onset diabetes of the young (HNF1A-MODY), other variants can be risk factors for the development of type 2 diabetes. As has been suggested by the American College of Medical Genetics (ACMG) guidelines for variant interpretation, functional studies provide strong evidence to classify a variant as pathogenic.

OBJECTIVE

We hypothesized that a functional evaluation can improve the interpretation of the HNF1A variants in our Czech MODY Registry.

DESIGN, SETTINGS, AND PARTICIPANTS

We studied 17 HNF1A variants that were identified in 48 individuals (33 female/15 male) from 20 Czech families with diabetes, using bioinformatics in silico tools and functional protein analyses (transactivation, protein expression, DNA binding, and nuclear localization).

RESULTS

Of the 17 variants, 12 variants (p.Lys120Glu, p.Gln130Glu, p.Arg131Pro, p.Leu139Pro, p.Met154Ile, p.Gln170Ter, p.Glu187SerfsTer40, p.Phe215SerfsTer18, p.Gly253Arg, p.Leu383ArgfsTer3, p.Gly437Val, and p.Thr563HisfsTer85) exhibited significantly reduced transcriptional activity or DNA binding (< 40%) and were classified as (likely) pathogenic, 2/17 variants were (likely) benign and 3/17 remained of uncertain significance. Functional analyses allowed for the reclassification of 10/17 variants (59%). Diabetes treatment was improved in 20/29 (69%) carriers of (likely) pathogenic HNF1A variants.

CONCLUSION

Functional evaluation of the HNF1A variants is necessary to better predict the pathogenic effects and to improve the diagnostic interpretation and treatment, particularly in cases where the cosegregation or family history data are not available or where the phenotype is more diverse and overlaps with other types of diabetes.

NPR2 Variants Are Frequent among Children with Familiar Short Stature and Respond Well to Growth Hormone Therapy

CONTEXT

The C-type natriuretic peptide receptor encoded by the NPR2 gene is a paracrine regulator of the growth plate; heterozygous NPR2 variants cause short stature with possible presence of different signs of bone dysplasia. To date, the effect of growth hormone (GH) treatment has been described in a few individuals with NPR2 gene variants with inconsistent results.

OBJECTIVES

To identify NPR2 gene variants among children with familial short stature (FSS) and to describe their phenotype, including GH treatment response.

DESIGN, SETTINGS AND PATIENTS

Out of 747 patients with short stature treated with GH in a single center, 87 with FSS met the inclusion criteria (pretreatment height ≤ -2 standard deviation in both the patient and the shorter parent, unknown genetic etiology). Next-generation sequencing methods were performed to search for NPR2 gene variants. The results were evaluated using the American College of Medical Genetics and Genomics guidelines. The GH treatment response (growth velocity improvement and height standard deviation score development over the first 5 years of treatment) was evaluated.

RESULTS

In 5/87 children (5.7%), a (likely) pathogenic variant in the NPR2 gene was identified (p.Ile558Thr [in 2], p.Arg205*, p.Arg557His, p.Ser603Thr). Two children had disproportionate short-limbed short stature, 1 a dysplastic 5th finger phalanx. The growth velocity in the first year of GH treatment accelerated by 3.6 to 4.2 cm/year; the height improved by 1.2 to 1.8 SD over 5 years of treatment.

CONCLUSIONS

NPR2 gene variants cause FSS in a significant proportion of children. Their GH treatment response is promising. Studies including final height data are necessary to assess the long-term efficacy of this therapy.

Screening of monogenic autoimmune diabetes among children with type 1 diabetes and multiple autoimmune diseases: is it worth doing?

Background Paediatric type 1 diabetes (T1D) and rare syndromes of monogenic multi-organ autoimmunity share basic features such as full insulin dependency and the presence of circulating beta-cell autoantibodies. However, the aetiopathogenesis, natural course and treatment of these conditions differ; therefore, monogenic multi-organ autoimmunity requires early recognition. We aimed to search for these monogenic conditions among a large cohort of children with T1D. Methods Of 519 children with T1D followed-up in a single centre, 18 had multiple additional autoimmune conditions - either autoimmune thyroid disease (AITD) and coeliac disease (CD) or at least one additional organ-specific autoimmune condition in addition to AITD or CD. These 18 children were tested by direct Sanger sequencing (four patients with a suggestive phenotype of immune dysregulation, polyendocrinopathy, enteropathy, X-linked [IPEX] or signal transducer and activator of transcription 3 [STAT3]- and cytotoxic T-lymphocyte protein 4 [CTLA4]-associated syndromes) or by whole-exome sequencing (WES) focused on autoimmune regulator (AIRE), forkhead box protein 3 (FOXP3), CTLA4, STAT3, signal transducer and activator of transcription 1 (STAT1), lipopolysaccharide-responsive and beige-like anchor protein (LRBA) and interleukin-2 receptor subunit α (IL2RA) genes. In addition, we assessed their T1D genetic risk score (T1D-GRS). Results We identified novel variants in FOXP3, STAT3 and CTLA4 in four cases. All patients had a severe phenotype suggestive of a single gene defect. No variants were identified in the remaining 14 patients. T1D-GRS varied among the entire cohort; four patients had scores below the 25th centile including two genetically confirmed cases. Conclusions A monogenic cause of autoimmune diabetes was confirmed only in four patients. Genetic screening for monogenic autoimmunity in children with a milder phenotype and a combination of AITD and CD is unlikely to identify a monogenic cause. In addition, the T1D-GRS varied among individual T1D patients.

High Prevalence of Growth Plate Gene Variants in Children With Familial Short Stature Treated With GH

CONTEXT

Familial short stature (FSS) is a term describing a growth disorder that is vertically transmitted. Milder forms may result from the combined effect of multiple genes; more severe short stature is suggestive of a monogenic condition. The etiology of most FSS cases has not been thoroughly elucidated to date.

OBJECTIVES

To identify the genetic etiology of severe FSS in children treated with GH because of the diagnosis of small for gestational age or GH deficiency (SGA/GHD).

DESIGN, SETTINGS, AND PATIENTS

Of 736 children treated with GH because of GHD/SGA, 33 with severe FSS (life-minimum height -2.5 SD or less in both the patient and shorter parent) were included in the study. The genetic etiology was known in 5 of 33 children prior to the study [ACAN (in 2], NF1, PTPN11, and SOS1). In the remaining 28 of 33, whole-exome sequencing was performed. The results were evaluated using American College of Medical Genetics and Genomics standards and guidelines.

RESULTS

In 30 of 33 children (90%), we found at least one variant with potential clinical significance in genes known to affect growth. A genetic cause was elucidated in 17 of 33 (52%). Of these children, variants in growth plate-related genes were found in 9 of 17 [COL2A1, COL11A1, and ACAN (all in 2), FLNB, FGFR3, and IGF1R], and IGF-associated proteins were affected in 2 of 17 (IGFALS and HMGA2). In the remaining 6 of 17, the discovered genetic mechanisms were miscellaneous (TRHR, MBTPS2, GHSR, NF1, PTPN11, and SOS1).

CONCLUSIONS

Single-gene variants are frequent among families with severe FSS, with variants affecting the growth plate being the most prevalent.

Short Stature in a Boy with Multiple Early-Onset Autoimmune Conditions due to a STAT3 Activating Mutation: Could Intracellular Growth Hormone Signalling Be Compromised?

BACKGROUND

Germline STAT3 gain-of-function (GOF) mutations cause multiple endocrine and haematologic autoimmune disorders, lymphoproliferation, and growth impairment. As the JAK-STAT pathway is known to transduce the growth hormone (GH) signalling, and STAT3 interacts with STAT5 in growth regulation, we hypothesised that short stature in STAT3 GOF mutations results mostly from GH insensitivity via involving activation of STAT5.

CASE REPORT

A boy with a novel STAT3 c.2144C>T (p.Pro715Leu) mutation presented with short stature (-2.60 SD at 5.5 years). He developed diabetes mellitus at 11 months, generalised lympho-proliferation, autoimmune thyroid disease, and immune bicytopenia in the subsequent years. At 5.5 years, his insulin-like growth factor-1 (IGF-I) was 37 µg/L (-2.22 SD) but stimulated GH was 27.7 µg/L. Both a standard IGF-I generation test (GH 0.033 mg/kg/day sc; 4 days) and a high-dose prolonged IGF-I generation test (GH 0.067 mg/kg/day sc; 14 days) failed to significantly increase IGF-I levels (37-46 and 72-87 µg/L, respectively). The boy underwent haematopoietic stem cell transplantation at 6 years due to severe neutropenia and massive lymphoproliferation, but unfortunately deceased 42 days after transplantation from reactivated generalised adenoviral infection.

CONCLUSIONS

Our findings confirm the effect of STAT3 GOF mutation on the downstream activation of STAT5 resulting in partial GH insensitivity. 
.

Could a combination of heterozygous ABCC8 and KCNJ11 mutations cause congenital hyperinsulinism?

BACKGROUND

Congenital hyperinsulinism (CHI) is frequently caused by mutations in one of the KATP channel subunits encoded by the genes ABCC8 and KCNJ11. The effect of simultaneous mutations in both of these genes on the pancreatic β-cell function is not known and patients with CHI carrying both ABCC8 and KCNJ11 mutations have not yet been reported. We questioned if a combination of heterozygous mutations in the ABCC8 and KCNJ11 genes could also lead to β-cell dysfunction presenting as CHI.

METHODS

As a model, we used a patient with transient CHI that paternally inherited novel heterozygous mutations in ABCC8 (p.Tyr1293Asp) and KCNJ11 (p.Arg50Trp) genes. The pathogenic effects on the pancreatic β-cells function were examined in an in vitro functional study using radioactive rubidium efflux assay.

RESULTS

We showed that the activation of the mutated KATP channels by diazoxide was decreased by 60.9% in the channels with the heterozygous combination of both mutations compared to the wild type channels. This could indicate the pathogenic effect on the pancreatic β-cell function leading to CHI although conclusive evidence is needed to be added.

CONCLUSIONS

Our findings may widen the spectrum of genetic causes of CHI and suggest a novel pathogenic mechanism of CHI that must however, be further investigated.

MODY in Ukraine: genes, clinical phenotypes and treatment

BACKGROUND

Maturity-onset diabetes of the young (MODY) has not been previously studied in Ukraine. We investigated the genetic etiology in a selected cohort of patients with diabetes diagnosed before 18 years of age, and in their family members.

METHODS

Genetic testing of the most prevalent MODY genes (GCK, HNF1A, HNF4A, HNF1B and INS) was undertaken for 36 families (39 affected individuals) by Sanger or targeted next generation sequencing.

RESULTS

A genetic diagnosis of MODY was made in 15/39 affected individuals from 12/36 families (33%). HNF1A and HNF4A MODY were the most common subtypes, accounting for 9/15 of MODY cases. Eight patients with HNF1A or HNF4A MODY and inadequate glycemic control were successfully transferred to sulfonylureas. Median HbA1c decreased from 67 mmol/mol (range 58-69) to 47 mmol/mol (range 43-50) (8.3% [7.5-8.5] to 6.4% [6.1-6.7]) 3 months after transfer (p=0.006).

CONCLUSIONS

Genetic testing identified pathogenic HNF1A and HNF4A variants as the most common cause of MODY in Ukraine. Transfer to sulfonylureas substantially improved the glycemic control of these patients.

Choledochal Cyst with 17q12 Chromosomal Duplication

The 17q12 chromosomal region carries the HNF1B gene, mutations of which cause various conditions. When searching for HNF1B/17q12 rearrangements among children with biliary atresia and/or choledochal cysts, we identified a male proband carrying a 17q12 duplication spanning 1698 kb that included 24 genes from TBC1D3C to HNF1B. The boy presented with cholestatic jaundice at the age of 2 weeks due to a choledochal cyst sized 15 ×12 mm (type Ia according to the Todani classification). He underwent a shunt surgery consisting of a hepaticojejunostomy using Roux-en-Y loop at the age of 2 months, which led to a permanent relief of cholestasis. Perioperative liver histology revealed significant hepatic fibrosis and bile ductular proliferation. At 17 years, he has a mildly enlarged liver with decreased elasticity, an upper-normal-sized spleen, normal biochemistry values, and no renal or hepatic cysts. We report the first hepatobiliary phenotype in a patient with an HNF1B overdosage.

Novel glucokinase gene mutation in the first Macedonian family tested for MODY

We present a boy with mild hyperglycemia detected during an upper respiratory infection. Novel splicing mutation in the intron 1 of the GCK gene (c.45+1G>A) was detected, and was subsequently confirmed in his father. This is the first case of genetically confirmed Macedonian family with MODY.

Combined pituitary hormone deficiency due to gross deletions in the POU1F1 (PIT-1) and PROP1 genes

Pituitary development depends on a complex cascade of interacting transcription factors and signaling molecules. Lesions in this cascade lead to isolated or combined pituitary hormone deficiency (CPHD). The aim of this study was to identify copy number variants (CNVs) in genes known to cause CPHD and to determine their structure. We analyzed 70 CPHD patients from 64 families. Deletions were found in three Turkish families and one family from northern Iraq. In one family we identified a 4.96 kb deletion that comprises the first two exons of POU1F1. In three families a homozygous 15.9 kb deletion including complete PROP1 was discovered. Breakpoints map within highly homologous AluY sequences. Haplotype analysis revealed a shared haplotype of 350 kb among PROP1 deletion carriers. For the first time we were able to assign the boundaries of a previously reported PROP1 deletion. This gross deletion shows strong evidence to originate from a common ancestor in patients with Kurdish descent. No CNVs within LHX3, LHX4, HESX1, GH1 and GHRHR were found. Our data prove multiplex ligation-dependent probe amplification to be a valuable tool for the detection of CNVs as cause of pituitary insufficiencies and should be considered as an analytical method particularly in Kurdish patients.

Substantial proportion of MODY among multiplex families participating in a Type 1 diabetes prediction programme

AIMS

Patients with maturity-onset diabetes of the young (MODY) might be over-represented in families with histories of Type 1 diabetes. Our aim was to re-evaluate families participating in the Czech T1D Prediction Programme (PREDIA.CZ) with at least two members affected with diabetes to assess the proportion of MODY among these families and determine its most significant clinical predictors.

METHODS

Of the 557 families followed up by the PREDIA.CZ, 53 (9.5%) had two or more family members with diabetes. One proband with diabetes from these families was chosen for direct sequencing of the GCK, HNF1A, HNF4A and INS genes. Non-parametric tests and a linear logistic regression model were used to evaluate differences between MODY and non-MODY families.

RESULTS

MODY was genetically diagnosed in 24 of the 53 families with multiple occurrences of diabetes (45%). Mutations were detected most frequently in GCK (58%), followed by HNF1A (38%) and INS (4%). MODY families were more likely to have a parent with diabetes and had a higher proportion of females with diabetes than non-MODY families. Higher age (P < 0.001), a lower level of HbA_1c (P < 0.001) at clinical onset and at least two generations affected by diabetes were the variables most predictive for probands of MODY families already presenting with diabetes.

CONCLUSIONS

A prediction programme for Type 1 diabetes would provide a useful new source of patients with MODY most likely to benefit from an accurate diagnosis. This identification has implications for patient treatment and disease prognosis.

The Common p.R114W HNF4A Mutation Causes a Distinct Clinical Subtype of Monogenic Diabetes

HNF4A mutations cause increased birth weight, transient neonatal hypoglycemia, and maturity onset diabetes of the young (MODY). The most frequently reported HNF4A mutation is p.R114W (previously p.R127W), but functional studies have shown inconsistent results; there is a lack of cosegregation in some pedigrees and an unexpectedly high frequency in public variant databases. We confirm that p.R114W is a pathogenic mutation with an odds ratio of 30.4 (95% CI 9.79-125, P = 2 × 10(-21)) for diabetes in our MODY cohort compared with control subjects. p.R114W heterozygotes did not have the increased birth weight of patients with other HNF4A mutations (3,476 g vs. 4,147 g, P = 0.0004), and fewer patients responded to sulfonylurea treatment (48% vs. 73%, P = 0.038). p.R114W has reduced penetrance; only 54% of heterozygotes developed diabetes by age 30 years compared with 71% for other HNF4A mutations. We redefine p.R114W as a pathogenic mutation that causes a distinct clinical subtype of HNF4A MODY with reduced penetrance, reduced sensitivity to sulfonylurea treatment, and no effect on birth weight. This has implications for diabetes treatment, management of pregnancy, and predictive testing of at-risk relatives. The increasing availability of large-scale sequence data is likely to reveal similar examples of rare, low-penetrance MODY mutations.

Novel calcium-sensing receptor cytoplasmic tail deletion mutation causing autosomal dominant hypocalcemia: molecular and clinical study

OBJECTIVE

Autosomal dominant hypocalcemia (ADH) is a rare disorder caused by activating mutations of the calcium-sensing receptor (CASR). The treatment of ADH patients with 1α-hydroxylated vitamin D derivatives can cause hypercalciuria leading to nephrocalcinosis.

DESIGN AND METHODS

We studied a girl who presented with hypoparathyroidism and asymptomatic hypocalcemia at age 2.5 years. Mutations of CASR were investigated by DNA sequencing. Functional analyses of mutant and WT CASRs were done in transiently transfected human embryonic kidney (HEK293) cells.

RESULTS

The proband and her father are heterozygous for an eight-nucleotide deletion c.2703_2710delCCTTGGAG in the CASR encoding the intracellular domain of the protein. Transient expression of CASR constructs in kidney cells in vitro suggested greater cell surface expression of the mutant receptor with a left-shifted extracellular calcium dose-response curve relative to that of the WT receptor consistent with gain of function. Initial treatment of the patient with calcitriol led to increased urinary calcium excretion. Evaluation for mosaicism in the paternal grandparents of the proband was negative.

CONCLUSIONS

We describe a novel naturally occurring deletion mutation within the CASR that apparently arose de novo in the father of the ADH proband. Functional analysis suggests that the cytoplasmic tail of the CASR contains determinants that regulate the attenuation of signal transduction. Early molecular analysis of the CASR gene in patients with isolated idiopathic hypoparathyroidism is recommended because of its relevance to clinical outcome and treatment choice. In ADH patients, calcium supplementation and low-dose cholecalciferol avoids hypocalcemic symptoms without compromising renal function.

High Incidence of Heterozygous ABCC8 and HNF1A Mutations in Czech Patients With Congenital Hyperinsulinism

CONTEXT

Congenital hyperinsulinism of infancy (CHI) represents a group of heterogeneous disorders characterized by oversecretion of insulin from pancreatic β-cells causing severe hypoglycemia.

OBJECTIVE

We studied the distribution of genetic causes of CHI in a Czech population.

METHODS

Countrywide collection of patients with CHI included 40 subjects (12 females, median age of diagnosis, 1 wk [interquartile range, 1-612 wk]). We sequenced the ABCC8, KCNJ11, GLUD1, GCK, HADH, UCP2, SLC16A1, HNF4A, and HNF1A genes and investigated structural changes in the ABCC8 gene. We functionally tested novel variants in the ABCC8 gene by Rb(86+) efflux assay and novel variants in the HNF1A gene by transcriptional activation and DNA-binding tests.

RESULTS

We found causal mutations in 20 subjects (50%): 19 carried a heterozygous mutation while one patient was homozygous for mutation in the ABCC8 gene. Specifically, we detected 11 mutations (seven novel) in ABCC8, one novel mutation in KCNJ11, five mutations (two novel) in HNF1A, two novel mutations in HNF4A, and one in GCK. We showed a decrease of activation by diazoxide in mutant KATP channels with novel ABCC8 variants by 41-91% (median, 82%) compared with wild-type (WT) channels and reduced transcriptional activity of mutant HNF1A proteins (2.9% for p.Asn62Lysfs93* and 22% for p.Leu254Gln) accompanied by no DNA-binding ability compared with WT HNF1A.

CONCLUSION

We detected a higher proportion of heterozygous mutations causing CHI compared with other cohorts probably due to lack of consanguinity and inclusion of milder CHI forms. Interestingly, HNF1A gene mutations represented the second most frequent genetic cause of CHI in the Czech Republic. Based on our results we present a genetic testing strategy specific for similar populations.

Hepatic phenotypes of HNF1B gene mutations: A case of neonatal cholestasis requiring portoenterostomy and literature review

Hepatocyte nuclear factor 1-β (HNF1B) defects cause renal cysts and diabetes syndrome (RCAD), or HNF1B-maturity-onset diabetes of the young. However, the hepatic phenotype of HNF1B variants is not well studied. We present a female neonate born small for her gestational age [birth weight 2360 g; -2.02 standard deviations (SD) and birth length 45 cm; -2.40 SD at the 38^th gestational week]. She developed neonatal cholestasis due to biliary atresia and required surgical intervention (portoenterostomy) when 32-d old. Following the operation, icterus resolved, but laboratory signs of liver dysfunction persisted. She had hyperechogenic kidneys prenatally with bilateral renal cysts and pancreatic hypoplasia postnatally that led to the diagnosis of an HNF1B deletion. This represents the most severe hepatic phenotype of an HNF1B variant recognized thus far. A review of 12 published cases with hepatic phenotypes of HNF1B defects allowed us to distinguish three severity levels, ranging from neonatal cholestasis through adult-onset cholestasis to non-cholestatic liver impairment, all of these are associated with congenital renal cysts and mostly with diabetes later in life. We conclude that to detect HNF1B variants, neonates with cholestasis should be checked for the presence of renal cysts, with special focus on those who are born small for their gestational age. Additionally, patients with diabetes and renal cysts at any age who develop cholestasis and/or exocrine pancreatic insufficiency should be tested for HNF1B variants as the true etiological factor of all disease components. Further observations are needed to confirm the potential reversibility of cholestasis in infancy in HNF1B mutation/deletion carriers.

Frameshift mutations in the insulin gene leading to prolonged molecule of insulin in two families with Maturity-Onset Diabetes of the Young

Mutations in the insulin (INS) gene rarely occur in patients with Maturity-Onset Diabetes of the Young (MODY). We aimed to describe in detail two MODY families with INS mutations. The INS gene was screened by direct sequencing. The probands and their affected relatives underwent a mixed-meal test. Mutation predictions were modeled using I-TASSER and were visualized by Swiss-PdbViewer. A novel heterozygous frameshift mutation p.Gln78fs in the INS gene was found in three generations of patients with clinically distinct diabetes. The single nucleotide deletion (c.233delA) is predicted to change and prolong amino acid sequence, resulting in aberrant proinsulin without native structures of C-peptide and A-chain. In the second family, the heterozygous mutation c.188-31G>A within the terminal intron was detected. The mother and her daughter were misdiagnosed as having type 1 diabetes since the ages of 6 and 2 years, respectively. This result is in contrast to the previously described carrier of the same mutation who was diagnosed with permanent neonatal diabetes. We identified a novel coding frameshift mutation and an intronic mutation in the INS gene leading to childhood-onset diabetes. INS mutations may result in various phenotypes, suggesting that additional mechanisms may be involved in the pathogenesis and clinical manifestation of diabetes.

Treated Autoimmune Thyroid Disease Is Associated with a Decreased Quality of Life among Young Persons with Type 1 Diabetes

Type 1 diabetes (T1D) in children and adolescents is relatively often accompanied by other immunopathological diseases, autoimmune thyroid disease (AITD) or celiac disease (CD). Our aim was to assess whether these conditions are associated with changes in the health-related quality of life (HRQOL) in pediatric patients with T1D. In a cross-sectional study we identified eligible 332 patients with T1D aged 8-18 years, of whom 248 (75%) together with their parents responded to the PedsQL Generic and Diabetes Modules. Compared to 143 patients without thyroid autoantibodies, 40 patients with a thyroxine-treated AITD scored lower in the overall generic HRQOL (P = 0.014), as well as in the overall diabetes-specific HRQOL (P = 0.013). After adjustment for age, gender, duration of diabetes, type of diabetes treatment, and diabetes control, this association remained statistically significant for the generic HRQOL (P = 0.023). Celiac disease was not associated with a change in the generic or diabetes-specific HRQOL (P = 0.07  and  P = 0.63, resp.). Parental scores showed no association with AITD or celiac disease, except a marginally significant decrease in the overall generic HRQOL (P = 0.039) in the T1D + AITD compared to T1D group. Our study indicates that, in pediatric patients with T1D, concomitant thyroxine-treated AITD is associated with lower quality of life.

Lessons from whole-exome sequencing in MODYX families

We report the first results from whole-exome sequencing performed in families with Maturity-Onset Diabetes of the Young without a known genetic cause of diabetes (MODYX). This next generation sequencing technique pointed out that routine testing of MODY needs constant awareness and regular re-evaluation of both clinical criteria and primer sequences.

De novo mutations of GCK, HNF1A and HNF4A may be more frequent in MODY than previously assumed

AIMS/HYPOTHESIS

MODY is mainly characterised by an early onset of diabetes and a positive family history of diabetes with an autosomal dominant mode of inheritance. However, de novo mutations have been reported anecdotally. The aim of this study was to systematically revisit a large collection of MODY patients to determine the minimum prevalence of de novo mutations in the most prevalent MODY genes (i.e. GCK, HNF1A, HNF4A).

METHODS

Analysis of 922 patients from two national MODY centres (Slovakia and the Czech Republic) identified 150 probands (16%) who came from pedigrees that did not fulfil the criterion of two generations with diabetes but did fulfil the remaining criteria. The GCK, HNF1A and HNF4A genes were analysed by direct sequencing.

RESULTS

Mutations in GCK, HNF1A or HNF4A genes were detected in 58 of 150 individuals. Parents of 28 probands were unavailable for further analysis, and in 19 probands the mutation was inherited from an asymptomatic parent. In 11 probands the mutations arose de novo.

CONCLUSIONS/INTERPRETATION

In our cohort of MODY patients from two national centres the de novo mutations in GCK, HNF1A and HNF4A were present in 7.3% of the 150 families without a history of diabetes and 1.2% of all of the referrals for MODY testing. This is the largest collection of de novo MODY mutations to date, and our findings indicate a much higher frequency of de novo mutations than previously assumed. Therefore, genetic testing of MODY could be considered for carefully selected individuals without a family history of diabetes.

Anophthalmia, hearing loss, abnormal pituitary development and response to growth hormone therapy in three children with microdeletions of 14q22q23

BACKGROUND

Microdeletions of 14q22q23 have been associated with eye abnormalities and pituitary defects. Other phenotypic features in deletion carriers including hearing loss and response to growth hormone therapy are less well recognized. We studied genotype and phenotype of three newly identified children with 14q22q23 deletions, two girls and one boy with bilateral anophthalmia, and compared them with previously published deletion patients and individuals with intragenic defects in genes residing in the region.

RESULTS

The three deletions were de novo and ranged in size between 5.8 and 8.9 Mb. All three children lacked one copy of the OTX2 gene and in one of them the deletion involved also the BMP4 gene. All three patients presented partial conductive hearing loss which tended to improve with age. Analysis of endocrine and growth phenotypes showed undetectable anterior pituitary, growth hormone deficiency and progressive growth retardation in all three patients. Growth hormone therapy led to partial catch-up growth in two of the three patients but just prevented further height loss in the third.

CONCLUSIONS

The pituitary hypoplasia, growth hormone deficiency and growth retardation associated with 14q22q23 microdeletions are very remarkable, and the latter appears to have an atypical response to growth hormone therapy in some of the cases.

The dynamic changes of zinc transporter 8 autoantibodies in Czech children from the onset of Type 1 diabetes mellitus

AIMS

The prevalence of autoantibodies to zinc transporter 8 (ZnT8) in Czech children at the onset of Type 1 diabetes mellitus and dynamic changes in ZnT8 autoantibody levels during disease progression were studied. The value of ZnT8 autoantibody measurements in diagnosis of Type 1 diabetes was assessed.

METHODS

Serum samples from 227 children with newly diagnosed Type 1 diabetes and from 101 control children without diabetes were analysed in a retrospective cross-sectional study. One hundred and seventy-one samples from 116 of the patients with diabetes were analysed in a follow-up study at (median) intervals of 1, 3, 5 and 10 years after onset of Type 1 diabetes. ZnT8 autoantibodies were measured using a bridging enzyme-linked immunosorbent assay, while antibodies to glutamic acid decarboxylase, insulinoma antigen 2 and insulin were measured by radioimmunoassays.

RESULTS

ZnT8 autoantibodies were detected in 163/227 (72%) of children at Type 1 diabetes onset and in 1/101 (1%) of the control subjects. Sixteen out of 227 (7%) patients with Type 1 diabetes were antibody negative based on three antibodies (glutamic acid decarboxylase, insulinoma antigen 2 and insulin). This false-negative rate was reduced to 10/227 (4.4%) (P < 0.05) after inclusion of ZnT8 autoantibody measurements. Of the children, 142/227 (63%) were positive for at least three antibodies and the most common combination was insulinoma antigen 2, glutamic acid decarboxylase and ZnT8. ZnT8 autoantibody levels decreased over time after Type 1 diabetes onset and the presence and level of ZnT8 autoantibodies correlated with IA-2 autoantibodies.

CONCLUSIONS

A ZnT8 autoantibody enzyme-linked immunosorbent assay showed 72% disease sensitivity and 99% specificity at Type 1 diabetes onset. Measurements of ZnT8 autoantibodies are important for Type 1 diabetes diagnosis and should be included in the panel of autoantibodies tested at the onset of Type 1 diabetes.

High prevalence of PROP1 defects in Lithuania: phenotypic findings in an ethnically homogenous cohort of patients with multiple pituitary hormone deficiency

CONTEXT

PROP1 gene mutations cause multiple pituitary hormone deficiency (MPHD).

OBJECTIVE

We sought to expand experience with PROP1 mutation carriers by studying a large cohort of Lithuanian patients.

PATIENTS AND METHODS

Sixty-seven MPHD patients were tested for PROP1 defects. Perinatal and postnatal data were obtained from medical records. Hormonal investigations, pituitary imaging, and GH therapy were provided in a single center in Kaunas, Lithuania.

RESULTS

A biallelic PROP1 gene mutation was found in 47 subjects (70.1%), of which 46 were homozygous for 296delGA. Positive finding rate among MPHD and population prevalence of PROP1 defects in Lithuania (15.8 per million) were the highest reported to date. Patients' birth lengths/weights were normal. Testicular retention was noted in 31% of boys. Median height SD scores declined over years 1-5: -1.56, -2.34, -3.43, -3.52, and -3.70. Mid-parental height predicted severity of growth retardation at diagnosis (r2=0.30; P=.0001). Deficiencies of GH, TSH, ACTH, and FSH/LH were diagnosed in 44/44, 44/44, 19/44, and 22/44 subjects at median age of 5.5, 5.6, 13.1, and 15.0 years, respectively. Pituitary height ranged from 16.6 mm (+20.2 SD) to 1.4 mm (-15.5 SD) and declined with age (r2=0.27, P=.001). GH replacement (dose 0.027 mg/kg/d) led to height velocities 12.2; 9.1; 6.9; 6.8; 6.7; 5.6; and 5.7 cm/y (medians) at years 1-7 and final height SD scores (17 patients) -0.98±1.77 (-1.04±1.41 below target height; P=.008 vs 0).

CONCLUSIONS

High prevalence of PROP1 defects in Lithuania is due to 296delGA mutation, suggesting a founder effect.

Two cases of diabetic ketoacidosis in HNF1A-MODY linked to severe dehydration: is it time to change the diagnostic criteria for MODY?

OBJECTIVE

Hepatocyte nuclear factor-1A maturity-onset diabetes of the young (HNF1A-MODY) is a monogenic form of diabetes caused by heterozygous mutations in HNF1A. Currently, a history of diabetic ketoacidosis (DKA) is an exclusion criterion for genetic testing for MODY.

HISTORY AND EXAMINATION

In this article, we describe two unrelated patients aged 17 and 24 years with severe DKA developed several years after the diagnosis of HNF1A-MODY.

INVESTIGATION

Both patients were treated with insulin, but their metabolic control was poor (HbA1c 15%, 140 mmol/mol and 13%, 119 mmol/mol, respectively) due to noncompliance and missed insulin injections. In both patients, DKA followed a course of recurrent vomiting with dehydration and prerenal acute kidney injury. Their glycemia, blood pH, and base excess at admission were 97 mmol/L [1,748 mg/dL], 6.80, and -33 mmol/L (patient 1) and 34 mmol/L [613 mg/dL], 7.03, and -14 mmol/L (patient 2).

CONCLUSIONS

This anecdotal observation supports the notion that a history of DKA does not exclude MODY.

Chronic Mild Hyperglycemia in GCK-MODY Patients Does Not Increase Carotid Intima-Media Thickness

Aim. GCK-MODY is an autosomal dominant form of diabetes caused by heterozygous mutations in the glucokinase gene leading to a lifelong mild hyperglycemia. The risk of macrovascular complications is considered low, but studies are limited. We, therefore, investigated the carotid intima-media thickness (CIMT) as an indicator of macrovascular complications in a group of patients with GCK-MODY. Methods. Twenty-seven GCK mutation carriers and 24 controls recruited among their first-degree relatives were compared, all aging over 35 years. The CIMT was tested using a high-resolution B-mode carotid ultrasonography. Medical history, anthropometry, and biochemical blood workup were obtained. Results. The mean CIMT was 0.707 ± 0.215 mm (mean ± SD) in GCK mutation carriers and 0.690 ± 0.180 mm in control individuals. When adjusted for age, gender, and family status, the estimated mean difference in CIMT between the two groups increased to 0.049 mm (P = 0.19). No difference was detected for other characteristics, with the exception of fasting blood glucose (GCK-MODY 7.6 mmol/L ± 1.2 (136.4 mg/dL); controls 5.3 mmol/L ± 0.3 (95.4 mg/dL); P < 0.0001) and glycated hemoglobin HbA1c (GCK-MODY 6.9% ± 1.0%, 52 mmol/mol ± 10; controls 5.7% ± 0.4%, 39 mmol/mol ± 3; P < 0.0001). The frequency of myocardial infarction and ischemic stroke did not differ between groups. Conclusion. Our data indicate that the persistent hyperglycemia in GCK-MODY is associated with a low risk of developing diabetic macrovascular complications.

HbA1c-based diabetes diagnosis among patients with glucokinase mutation (GCK-MODY) is affected by a genetic variant of glucose-6-phosphatase (G6PC2)

AIMS

Genetic variation at the rs560887 locus of the glucose-6-phosphatase, catalytic 2 gene (G6PC2) is known to affect regulation of fasting glycaemia. We determined the rs560887 genotype of patients with monogenic diabetes and glucokinase gene mutations (GCK-MODY) and correlated the genotypes with HbA(1c) levels.

METHODS

Patients from families with GCK-MODY were recruited from two large cohorts from Poland (n = 128) and the Czech Republic (n = 154). Genotypes at the rs560887 polymorphic site in G6PC2 were examined using real-time quantitative polymerase chain reaction. The effect of rs560887 genotype on age at diagnosis of GCK-MODY and initial HbA(1c) levels were evaluated separately within both cohorts. Following that, a meta-analysis of rs560887 genotype-HbA(1c) associations of both Polish and Czech cohorts was performed to confirm homogeneity of findings and validate cohort-specific results.

RESULTS

GG homozygosity at rs560887 was associated with marginally elevated HbA(1c) levels (P = 0.07 in both cohorts). The effects observed in both groups were very homogeneous (Q = 0.18; P = 0.68). Meta-analysis showed that GG homozygosity at rs560887 was associated with mean HbA(1c) levels higher by 2.4 mmol/mol (0.24%), 95% CI 0.5-4.4 mmol/mol (0.05-0.44%) than in individuals with other genotypes. Additionally, meta-analysis of both cohorts showed that GG homozygous individuals had higher odds of reaching the 48 mmol/mol (6.5%) diagnostic threshold of diabetes; (odds ratio 1.90; 95% CI 1.07-3.36; P = 0.03). No such effects were observed for age at diagnosis of diabetes.

CONCLUSIONS

Variation at the rs560887 locus of G6PC2 is associated with worse glycated haemoglobin levels in individuals with GCK mutations; GG homozygotes are more likely to meet diagnostic criteria for diabetes based on HbA(1c) level.

Ancestral mutations may cause a significant proportion of GCK-MODY

BACKGROUND

Although the literature indicates that ancestral mutations in the glucokinase (GCK) gene are rare, we have detected a high frequency of four prevalent mutations that together are responsible for over one third of the GCK mutations in our Czech National Register of monogenic diabetes. Therefore, we studied their potential ancestral origin in our and neighbouring Polish populations.

METHODS

We analysed the lineage of four mutations in the GCK gene - p.Glu40Lys (21 apparently unrelated families), p.Leu315His (15 families), p.Gly318Arg (26 families), and p.Val33Ala (10 families) - using genotypes of 16 single nucleotide polymorphisms that span a 14 Mb region around the gene. Haplotypes were reconstructed using Phase and Haploview programmes, and their age was estimated using dmle+.

RESULTS

We found strong evidence that supports ancestral origin of three of the four mutations: the p.Glu40Lys mutation was associated with an 11-marker long conserved haplotype, the p.Leu315His mutation was associated with a 7-marker haplotype, and the p.Gly318Arg mutation was associated with an 8-marker haplotype. None of these haplotypes were detected in the general population with a frequency >0.5%. The ages of the mutations were roughly estimated to be between 82 and 110 generations old (95% credible sets 65-151). The fourth prevalent mutation, p.Val33Ala, lacked statistically significant evidence for the founder effect, although there were some indications for its common origin.

CONCLUSIONS

The large proportion of families carrying three ancestral mutations in GCK indicates that the previously assumed rarity of the founder effect with regard to GCK-maturity onset diabetes of the young (MODY) should be reconsidered.

Two independent genetic factors responsible for the associations of the IBD5 locus with Crohn's disease in the Czech population

BACKGROUND

The role of the IBD5 locus in development of Crohn's disease (CD) has not been clarified. In the Czech population we examined its genetic association using variants of the SLC22A4 (rs1050152), SLC22A5 (rs2631367), two single nucleotide polymorphisms (SNPs) shown to be associated with CD in genome-wide studies (rs6596075 and rs2188962), and four SNPs previously shown to tag the haplotype blocks 4, 7, 9, 10 of the IBD5 locus (IGR2063b_1, IGR2230a_1, IGR100Xa_1, IGR3236a_1).

METHODS

The genotype, phenotype, and allelic frequencies were compared between 469 unrelated patients with CD (177 pediatric-onset, 292 adult-onset) and 470 unrelated healthy controls, all Caucasians of Czech ancestry.

RESULTS

The most significant difference between patients and controls was found for the SNP rs6596075 (odds ratio [OR] = 0.70 for the G allele; 95% CI 0.52-0.94) in the dominant model and SNP IGR2063b_1 (OR = 1.38 for the G allele; 95% CI 1.14-1.67) in the log-additive model. We found a strong linkage disequilibrium across the IBD5 locus except rs6596075. The haplotype consisting of minor alleles of all tested SNPs except rs6596075 was carried by 31% patients and 23% control subjects (OR = 1.35, 95% CI 1.06-1.72). The association of variants in SLC22A4 and SLC22A5 was dependent on this risk haplotype, while the strong association of the rs6596075 was seemingly independent. In the analysis of subphenotypes we found only an association of the penetrating disease with rs6596075 (OR = 2.13; 95% CI 1.31-3.47).

CONCLUSIONS

Our study confirms the importance of IBD5 in determining CD susceptibility, and demonstrates that two independent genetic factors may be responsible for the association observed within this locus.

SNPman: a program for genotype calling using run data from TaqMan allelic discrimination

SUMMARY

The SNPman program calls the genotypes of single nucleotide polymorphisms (SNP) from TaqMan allelic discrimination assays. It utilizes the fluorescence data collected over the whole PCR run, rather than relying on the end point fluorescence measurements that is the basis of the genotype calling process in most software solutions sold with the real-time instruments. This inspection of run data facilitates genotype calls in difficult sample sets, especially in those containing various concentrations of DNA or inhibitors, as indicated by results of a reanalysis of 3738 genotyping samples. The program works with data from three different widely used PCR instruments.

AVAILABILITY

The compiled program is available online at http://sourceforge.net/projects/snpman/files/, along with its user documentation and demonstration data files. It is free of charge for non-commercial users.

CONTACT

Ondrej.Cinek@Lfmotol.cuni.cz

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Familial mild hyperglycemia associated with a novel ABCC8-V84I mutation within three generations

We present a unique case of a 19-year-old man with a positive family history of persistent mild hyperglycemia and a novel V84I mutation in ABCC8. The proband was initially detected to have fasting hyperglycemia (ranging 6.1-6.4 mmol/L) at the age of 12 years. Increased fasting blood glucose was also subsequently detected in five additional family members (in his twin brother, sister, mother, maternal aunt, and grandfather). The grandfather has been known to have mild diabetes since 30 years and has never been treated. After having excluded a causative mutation in five maturity-onset diabetes of the young genes (MODY1-4 and 6), we identified a novel ABCC8 V84I mutation, which segregated with autosomal dominant transmission of mild hyperglycemia within three generations. This mutation that is located in a conserved area of transmembrane domain TMD0 seems to be a rare cause of clinical phenotype resembling glucokinase-deficient diabetes.

HNF1A mutation presenting with fetal macrosomia and hypoglycemia in childhood prior to onset of overt diabetes

BACKGROUND

HNF1A-MODY (MODY3) is a common subtype of autosomal dominant diabetes. Unlike HNF4-MODY where fetal macrosomia and early postnatal hyperinsulinemic hypoglycemia have been reported, history of transient insulin overproduction has not yet been recognized in individuals with HNF1A-MODY.

CASE REPORT

Here, we report on a 40-year-old male patient with HNF1A mutation p.Arg272His (c.815G>A) having a history of fetal macrosomia (4750 g, 59 cm), and, at least, one attack of symptomatic hypoglycemia in childhood. Diabetes was subsequently diagnosed at 19 years of age. The proband's daughter who developed diabetes at 16 years carries the same mutation, but her birth weight and length were in the upper normal range, and she never experienced hypoglycemic symptoms.

CONCLUSION

The observation of fetal macrosomia and hypoglycemia in childhood is indicative of a biphasic impact of the HNF1A mutation on p-cell function over the lifespan, leading from inappropriate insulin oversecretion to final clinical diabetes.

Glucokinase diabetes in 103 families from a country-based study in the Czech Republic: geographically restricted distribution of two prevalent GCK mutations

BACKGROUND

Glucokinase diabetes, also called GCK-MODY or maturity-onset diabetes of the young type 2 (MODY2), is caused by heterozygous mutations in the gene encoding glucokinase (GCK).

OBJECTIVE

The aim of study was to investigate the current prevalence of GCK mutations in a large cohort of Czech patients with typical clinical appearance of GCK-MODY. In addition, we reanalyzed the negative results obtained previously by screening using the denaturing high-performance liquid chromatography (dHPLC).

METHODS

We studied 140 unrelated Czech probands with clinical picture of GCK-MODY who were referred to our center from the whole of the Czech Republic between the years 1999-2009 by direct sequencing of GCK gene.

RESULTS

A mutation in GCK was identified in 103 of 140 probands (74%). We identified 46 different GCK mutations of which 13 were novel. Several mutations were detected in multiple families: p.Glu40Lys (20 families), p.Gly318Arg (12), p.Leu315His (7) and p.Val33Ala (six families). Direct sequencing detected a GCK mutations in 9 of 20 previously dHPLC-negative samples; the sensitivity of the dHPLC screening was calculated as 84%.

CONCLUSIONS

The study shows a relatively high proportion of GCK mutations among individuals with GCK-like phenotype, confirming the effectiveness of carefully applied clinical criteria prior to genetic testing. In the Czech MODY registry, GCK-MODY represents the biggest subgroup of MODY (35%). We report several prevalent GCK mutations with a likely founder effect in the Czech population. Furthermore, our results provide ground for a possible recommendation to reinspect all negative results previously obtained by screening using dHPLC.

The CTLA4 variants may interact with the IL23R- and NOD2-conferred risk in development of Crohn's disease

BACKGROUND

The CTLA4 (cytotoxic T-lymphocyte antigen 4) gene is associated with several immunopathologic diseases and because of its important immuno-regulatory role it may be considered also a plausible candidate for a genetic association with inflammatory bowel diseases. Previously published studies found no association of CTLA4 with Crohn's disease itself, but some indicated an association with its subphenotypes. The aim of this study was to assess the association in the Czech population, using a set of markers shown to associate with other diseases.

METHODS

Six polymorphisms within the CTLA4 region were investigated in 333 patients with Crohn's disease and 482 unrelated healthy controls, all Caucasians of Czech origin. The genotypes of the SNPs were determined using the TaqMan SNP genotyping assays. Haplotypes were reconstructed using an expectation-maximization algorithm, and their association with the condition was assessed using log-linear modeling. Then, potential interactions were tested between the CTLA4 variants and other genetic factors known to confer the disease susceptibility.

RESULTS

No crude associations with Crohn's disease were found for the tested CTLA4 variants under the log-additive or dominant models. However, when stratified for the genetic risk conferred by the variants in the NOD2 (the p.Leu1007fsX1008, rs5743293) or the IL23R (p.R381Q, rs11209026), a significant negative association emerged for the minor alleles of CTLA4 CT60 (rs3087243), JO31 (rs11571302), JO27-1 (rs11571297) polymorphisms. This negative association with CTLA4 was apparent only in the strata defined by presence minor alleles at the NOD2 rs5743293 (here the CTLA4 CT60 A coffered an OR = 0.43, 95%CI 0.19 - 0.95 for the presence of CT60 A), or IL23R rs11209026 (here the OR for presence of CT60 A was 0.23, 95%CI 0.07 - 0.71). We observed this effect also for the haplotype consisting of minor alleles of the three tightly linked CTLA4 markers. Furthermore, this haplotype was associated with the younger age at diagnosis (OR 1.52, 95%CI 1.09 - 2.11, p = 0.014).

CONCLUSIONS

A protective effect of a CTLA4 haplotype was unmasked after stratification for the risk variants in the NOD2 and IL23R genes, and may point towards the biological relevance of the molecule in the pathogenesis of the disease.