Identification of a broad spectrum of mammalian and avian species using the short fragment of the mitochondrially encoded cytochrome b gene.

Mitochondrial DNA (mtDNA), especially the gene for cytochrome b (MT-CYB), has been found to be highly informative for species identification. In this study, we present the results of the analysis of a 127 bp long fragment of MT-CYB, amplified using universal primers, variable enough to be used for species identification and discrimination, even in highly degraded animal samples. The total number of analyzed species in this study was 30, including 17 mammalian and 13 bird species. Using a newly created primer pair, we successfully amplified and sequenced the target sequence in almost all tested species. The amplification was incomplete in just two species, and as a result, partial, but still variable sequences, were obtained. Using the target fragment we successfully identified all tested samples. Initial results suggested that the intraspecies genetic diversity of the target region, in all tested species, was low - from 0 to 4.72%. The interspecies genetic diversity of the target region, crucial for successful discrimination, showed relatively high diversity, ranging from 8.36% to 42.52%. Given its short length, the target region should be used for species determination, particularly in samples that are degraded or are low in DNA quantity.

Analysis of PMP22 duplication and deletion using a panel of six dinucleotide tandem repeats.

BACKGROUND: Charcot-Marie-Tooth type 1A (CMT1A) is the most common type of hereditary motor and sensory neuropathies (HMSN), caused by the duplication of the 17p11.2 region that includes the PMP22 gene. Reciprocal deletion of the same region is the main cause of hereditary neuropathy with liability to pressure palsies (HNPP). CMT1A accounts for approximately 50% of HMSN patients. Diagnostics of CMT1A and HNPP are based on quantitative analysis of the affected region or RFLP detection of breakage points. The aim of this study was to improve the sensitivity and efficiency of CMT1A and HNPP genetic diagnostics by introducing analysis of six STR markers (D17S261-D17S122-D17S839-D17S1358-D17S955-D17S921) spanning the duplicated region. METHODS: Forty-six CMT1A and seven HNPP patients, all genetically diagnosed by RFLP analysis, were tested for duplication or deletion using six STR markers. RESULTS: In all CMT1A and HNPP patients, microsatellite analysis comprising six STR markers confirmed the existence of a duplication or deletion. In 89% (41/46) CMT1A patients the confirmation was based on detecting three alleles on at least one locus. In the remaining 11% (5) CMT1A patients, duplication was also confirmed based on two peaks with clear dosage difference for at least two different markers. All HNPP patients (7/7) displayed only one allele for each analyzed locus. CONCLUSIONS: Microsatellite analysis using six selected STR loci showed a high level of sensitivity and specificity for genetic diagnostics of CMT1A and HNPP. The results here strongly suggest STR marker analysis as a method of choice in PMP22 duplication/deletion testing.

Comparison of the ABC and ACMG systems for variant classification.

The ABC and ACMG variant classification systems were compared by asking mainly European clinical laboratories to classify variants in 10 challenging cases using both systems, and to state if the variant in question would be reported as a relevant result or not as a measure of clinical utility. In contrast to the ABC system, the ACMG system was not made to guide variant reporting but to determine the likelihood of pathogenicity. Nevertheless, this comparison is justified since the ACMG class determines variant reporting in many laboratories. Forty-three laboratories participated in the survey. In seven cases, the classification system used did not influence the reporting likelihood when variants labeled as "maybe report" after ACMG-based classification were included. In three cases of population frequent but disease-associated variants, there was a difference in favor of reporting after ABC classification. A possible reason is that ABC step C (standard variant comments) allows a variant to be reported in one clinical setting but not another, e.g., based on Bayesian-based likelihood calculation of clinical relevance. Finally, the selection of ACMG criteria was compared between 36 laboratories. When excluding criteria used by less than four laboratories (<10%), the average concordance rate was 46%. Taken together, ABC-based classification is more clear-cut than ACMG-based classification since molecular and clinical information is handled separately, and variant reporting can be adapted to the clinical question and phenotype. Furthermore, variants do not get a clinically inappropriate label, like pathogenic when not pathogenic in a clinical context, or variant of unknown significance when the significance is known.

Distribution of Y-chromosome haplogroups in Serbian population groups originating from historically and geographically significant distinct parts of the Balkan Peninsula.

Our study enrolled 1200 Serbian males originating from three geographical regions in the Balkan Peninsula inhabited by Serbs: present-day Serbia, regions of Old Herzegovina and Kosovo and Metohija. These samples were genotyped using the combination of 23 Y-chromosomal short tandem repeats (Y-STRs) loci and 17 Ychromosomal single nucleotide polymorphisms (Y-SNPs) loci for the haplotype and haplogroup analysis in order to characterize in detail Y chromosome flow in the recent history. Serbia's borders have changed through history, forcing Serbs constantly to migrate to different regions of Balkan Peninsula. The most significant migration waves in the recent history towards present-day Serbia occurred from the regions of Old- Herzegovina and Kosovo and Metohija that lie in the south-west/south. High haplotype diversity and discrimination capacity were observed in all three datasets, with the highest number of unique haplotypes (381) and discrimination capacity (0.97) detected in the samples originating from the present-day Serbia. Haplogroup composition didn't differ significantly among datasets, with three dominant haplogroups (I-M170, E-P170 and R-M198), and haplogroup I-M170 being the most frequent in all three datasets. Haplogroup E-P170 was the second most dominant in the dataset originating from geographical region of Kosovo and Metohija, whereas haplogroup R-M198 was the second most prevalent in the dataset from historical region of Old Herzegovina. Based on the phylogenetic three for haplogroup I constructed within this study, haplogroup I2a1-P37.2 was the most dominant within all three datasets, especially in the dataset from historical region of Old Herzegovina, where 182 out of 400 samples were derived for SNP P37.2. Genetic distances between three groups of samples, evaluated by the Fst and Rst statistical values, and further visualized through multidimensional scaling plot, showed great genetic similarity between datasets from Old Herzegovina and present-day Serbia. Genetic difference in the haplogroup distribution and frequency between datasets from historical region of Old Herzegovina and from geographical region of Kosovo and Metohija was confirmed with highest Fst and Rst vaules. In this study we have distinguished genetic structure, diversity and haplogroup frequencies within 1200 Serbian males from three datasets, relationships among them as well as with other Balkan and European populations, which is useful for studying recent demographic history.