Katarina Štingl

Steroid 11-beta hydroxylase deficiency caused by compound heterozygosity for a novel mutation in intron 7 (IVS 7 DS+4A to G) in one CYP11B1 allele and R448H in exon 8 in the other

Congenital adrenal hyperplasia (CAH) due to steroid 11-beta hydroxylase deficiency (11β-OHD) is a rare genetic disorder of steroidogenesis transmitted as an autosomal recessive trait. We describe a new case of 11β-OHD CAH caused by compound heterozygosity for a novel mutation in intron 7 and previously described mutation in exon 8 of CYP 11B1 gene. A 2.5-year-old boy of Croatian descent presented with accelerated growth and bone age, borderline hypertension, and pseudoprecocious puberty. Hormonal studies established diagnosis of 11β-OHD: elevated plasma levels of 11-deoxycortisol, 17-hydroxyprogesterone, androstenedione and testosterone, low levels of cortisol and aldosterone, and suppressed plasma renin activity. Sequencing of the CYP11B1 gene identified compound heterozygous mutation consisting of a novel splicing mutation in intron 7 (IVS 7DS+4A to G) and R448H mutation in exon 8 previously reported mostly in Moroccan Jews. This is the first patient with CAH due to 11β-OHD in Croatia (and Slavic population in general) in whom molecular diagnosis of CYP11B1 gene was performed.

High resolution definition of HLA‐DRB haplotypes by a simplified microsatellite typing technique

In humans, the region configurations DR1, DR8, DR51, DR52 and DR53 are known to display copy number as well as allelic variation, rendering high resolution typing of HLA-DRB haplotypes cumbersome. Advantage was taken of microsatellite D6S2878, present in all DRB genes/pseudogenes with an intact exon 2-intron 2 segment. This DRB-STR is highly polymorphic in composition and length. Recently, it was proven that all exon 2 sequences could be linked to a certain DRB-STR that segregates with the respective DRB allele. Because haplotypes show differential copy numbers and compositions of exon 2-positive DRB genes/pseudogenes, unique DRB-STR patterns could be described that appear to be specific for a particular DRB haplotype. The aim of this workshop project was to approve and to qualify this simple typing protocol in a larger panel covering different European populations. All participants succeeded in correctly defining the DRB-STR amplicons varying from 135 to 222 base pair (bp) lengths. The panel of 101 samples covered 50 DRB alleles distributed over 37 different haplotypes as defined by exon 2 sequence-based typing. These haplotypes could be refined into 105 haplotypes by DRB-STR typing. Thus, discrimination of exon 2-identical DRB alleles was feasible, as well as the exact description of three different crossing-over events that resulted in the generation of hybrid DR region configurations. This typing procedure appears to be a quick and highly robust technique that can easily be performed by different laboratories, even without experience in microsatellite typing; thus, it is suitable for a variety of researchers in diverse research areas.

Classical Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency in Croatia between 1995 and 2006

Aims: To evaluate the incidence, gender, symptoms and age at diagnosis among patients with classical congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency in Croatia. Methods: Data were collected retrospectively for all classical CAH patients born or electively aborted following prenatal diagnosis between 01.01.1995 and 31.12.2006 and were compared with the data of the previously conducted study evaluating CAH patients discovered between 1964 and 1984. Results: During a 12-year period, 34 classical CAH patients were born. There were 20 salt-wasting (SW) (12 females/8 males) and 14 simple virilizing (SV) patients (7 females/7 males). If 3 female fetuses, electively aborted, were added, that would be a total of 37 CAH patients. With 532,942 live births and 34 CAH patients born over this period, incidence of classical CAH was estimated to 1:15,574 or 1:14,403 if 3 electively aborted fetuses were included. The lower incidence of SW boys compared to SW girls (8:12) and similar number of SW and SV boys (8:7) indicate that substantial proportion of SW boys die unrecognized. Owing to better health care, diagnosis was established significantly earlier in SW and SV girls compared to the period of 1964–1984 (p < 0.003). During 1995–2006, none of the patients died following the diagnosis of CAH, and there was no erroneous sex assignment. Conclusion: Despite of improvement in health care, diagnosis of CAH in Croatia is still delayed and some of the patients go unrecognized or die. Therefore, we think that the results of our study support the need for the introduction of newborn screening.

STR and HLA analysis in paternity testing

Abstract During the 3-year period, 111 cases of paternity disputes were processed in our laboratory. The analysis was performed on nine STR (TH01, VWA31, FES/FPS, F13A01, SE33, D1S1656, D12S391, D18S535, and D22S683) loci and one VNTR (D1S80) locus. Out of 111 cases, 22 were exclusions. In all cases, exclusion was confirmed on at least five loci. STR loci that were informative in majority of cases were SE33 and D12S391. The least informative loci were FES/FPS and F13A01. In 21 cases exclusions were also confirmed by HLA class I, while only in 17 cases HLA class II alleles excluded the alleged father.

Distribution of KIR genes in the Croatian population

The KIR locus with genes involved in immune processes is among the most polymorphic and structurally diverse human loci. KIR genes encode activating and inhibitory receptors that differ in specificity for HLA class I ligands and signaling potential. These receptors are expressed principally by natural killer (NK) cells and subpopulations of T cells. This study represents the first report of the distribution of KIR genes, KIR genotypes and KIR/HLA pairs in 121 unrelated healthy Croatian individuals. Twenty-three different genotypes were observed in the Croatian population and all 16 KIR genes known to date were found. The most frequent KIR genotype was the AA genotype. All individuals had at least one inhibitory KIR/HLA pair with the majority of individuals with three inhibitory KIR/HLA pairs. The most frequent KIR/HLA pair was the KIR2DL3/C1 group. Our results demonstrated the similarity of the Croatian populations KIR repertoire with other Caucasian populations reported so far.

The study of the extended haplotypes of rare HLA-B*2730 allele using microsatellite loci

The aim of the present study was to compare haplotypes of the most frequent B*27 alleles among Croatians (B*2702 and *2705) and the rare B*2730 allele. For this purpose, 37 families with members carrying human leukocyte antigen (HLA)-B27 were selected. All individuals were analysed for eight microsatellites (Msats): D6S2927, short tandem repeat - MHC class I-related gene (STR_MICA), D6S2793, D6S2811, tumor necrosis factor a (TNFa), tumor necrosis factor d (TNFd), D6S273 and D6S1014, while individuals carrying the HLA-B27 specificity were subtyped. Of 39 analysed haplotypes, 20 individuals had B*2702, 15 subjects were positive for the B*2705 allele, the B*2730 allele was found in three haplotypes from different families, while one individual carried the B*2703 allele. HLA-A3 and -DRB1*16 were shared by all three B*2730 haplotypes. The DRB1*16 allele was also observed in the majority of B*2702 haplotypes (76.5%), while HLA-A3 was, after HLA-A2, the second most frequent HLA-A specificity in B*2702 haplotypes. No such correlation was found for the B*2705 haplotypes. Msat analysis showed that B*2730 haplotypes also share the same allele at all tested Msats. The D6S2927, D6S2793, MICA and TNFd Msats were not useful in distinguishing B*2702 and B*2705 alleles because D6S2927-213bp, STR_MICA-179bp, D6S2793-206bp, D6S2811-83bp and TNFd-130bp were detected in almost all cases. Conversely, for the TNFa, D6S273 and D6S1014 loci, haplotypes carrying B*2702 and B*2730 shared a single Msat allele in the majority of cases (TNFa-113bp, D6S1014-134bp and D6S273-134bp), which was not observed for B*2705 haplotypes. In conclusion, the similarity between B*2702 and B*2730 DNA sequences as well as their sharing of the same haplotypic combinations corroborates the proposed mechanism of B*2730 evolution from B*2702 by interallelic recombination.

Repetitive DNA polymorphisms in following chimerism after allogeneic bone marrow transplantation

Abstract:  Information about the chimeric status of patients is of great importance in comparison of different conditioning and prophylactic regimens as well as for the post‐bone marrow transplantation (BMT) therapies. In some cases, mixed chimerism (MC) can also be predictive of relapse. Analysis of the short tandem repeats (STR) loci by polymerase chain reaction (PCR) is a choice method for this purpose. In this study, we monitored 15 patients after BMT. Twelve of them underwent classical‐conditioning regimen while the remaining three patients were subjected to non‐myeloablative conditioning (minitransplantation). Evaluation of chimerism was performed using five STR and one variable number of tandem repeats (VNTR) locus. Four additional loci were PCR‐amplified in cases of minitransplantation. Samples were analyzed by electrophoresis in an ALFexpress sequencer. MC was detected in seven cases of which it was predictive of relapse for two patients, who suffered from acute lymphocytic leukemia (ALL). The PCR‐STR method proved to be a fast and relatively simple method, while the tested STR loci showed a high level of informativeness.

Diversity of HLA-B*35 Alleles and Haplotypes among Croatians

Objectives: Investigation of HLA-B*35 subtypes and haplotypes among Croatians. Methods: 4000 randomly selected unrelated donors from Croatian Bone Marrow Donor Registry were typed for HLA-A, -B and -DRB1 by PCR-LabType®SSO method. Results: Four different B*35 alleles (*35:01, *35:02, *35:03, *35:08) were found. Three of them were with similar frequencies as in other European Caucasians, while HLA-B*35:03 was two times more frequent in our population. Predicted haplotypes were also in accordance with present data from other populations. Conclusions: This study should be of benefit in the unrelated haematopoietic stem cell transplantation (HSCT) program. It should facilitate the recipient-donor matching and the selection of a suitable population for further searches.

Application of microsatellite loci on the chromosome X for rapid prenatal detection of the chromosome X numerical abnormalities.

Aim To determine the value of short-tandem repeat markers on the chromosome X (X-STR) for prenatal diagnostics of the chromosome X numerical disorders. Methods We investigated the genetic variability of 5 X-markers (DXS9895, DXS6810, DXS6803, GATA172D05, and HPRTB) in 183 healthy Croatian individuals (90 men and 93 women). We also tested 13 patients with X chromosome disorders (Turner syndrome – 6 cases; Klinefelter syndrome – 5 cases, and Triple X syndrome – 2 cases). The analysis was performed using polymerase chain reaction amplification with specific primers and electrophoresis on a polyacrylamide gel. The study was performed in 2010. Results Our sample showed no significant differences in allelic frequencies of the investigated X-markers from other European populations. A set of 5 X-STR markers was sufficiently informative for a successful determination of the chromosome X numerical abnormalities. Conclusion Since no false positive or negative results were observed, diagnostic value of the investigated X-STR loci for prenatal detection of chromosome X numerical disorders was confirmed. Our study represents an important step toward an improved prenatal diagnostics in Croatia.

Heterogeneity of HLA‐DRB1*04 alleles and haplotypes in the Croatian population

Analysis of allele distribution at the HLA-DRB1*04 gene, as one of the frequent ones among Croatians, and their HLA-A-B-DRB1 haplotypes in the Croatian population was performed in this study. Using LABType® SSO and PCR-SSP method, 11 DRB1*04 subtypes were observed, of which DRB1*04:01 was the most frequent (28.0%) followed by DRB1*04:02 (26.3%), DRB1*04:03 (22.3%), and DRB1*04:04 (14.2%). The significant haplotypes (with highest P value) for given DRB1*04 allele were the following combinations: HLA-B*15:01-DRB1*04:01, HLA-B*38:01-DRB1*04:02, HLA-B*35:03-DRB1*04:03, HLA-B*35:03-DRB1*04:08, HLA-B*14:01-DRB1*04:04, and HLA-B*49-DRB1*04:05. Marked differences in the distribution of our most frequent haplotypes of HLA-B-DRB1*04 (HLA-B*38:01-DRB1*04:02 and HLA-B*15:01-DRB1*04:01) were found in comparison to other European populations investigated so far. Additionally, comparison of HLA-A-B-DRB1*04 haplotypes showed that although there are similarities in the haplotype structure between our and other populations, there are also noteworthy differences. In summary, the identification of conserved and unusual DRB1*04 haplotypes in the present study of Croats should have important clinical implications for donor-recipient matching in the hematopoietic stem cell transplantation program, help in the understanding of HLA polymorphisms in different European populations, and also prove to be very useful in the determination of possible susceptibility genes involved in HLA-DRB1*04-associated diseases.