Sex-biased patterns shaped the genetic history of Roma

The Roma population is a European ethnic minority characterized by recent and multiple dispersals and founder effects. After their origin in South Asia around 1,500 years ago, they migrated West. In Europe, they diverged into ethnolinguistically distinct migrant groups that spread across the continent. Previous genetic studies based on genome-wide data and uniparental markers detected Roma founder events and West-Eurasian gene flow. However, to the best of our knowledge, it has not been assessed whether these demographic processes have equally affected both sexes in the population. The present study uses the largest and most comprehensive dataset of complete mitochondrial and Y chromosome Roma sequences to unravel the sex-biased patterns that have shaped their genetic history. The results show that the Roma maternal genetic pool carries a higher lineage diversity from South Asia, as opposed to a single paternal South Asian lineage. Nonetheless, the European gene flow events mainly occurred through the maternal lineages; however, a signal of this gene flow is also traceable in the paternal lineages. We also detect a higher female migration rate among European Roma groups. Altogether, these results suggest that sociocultural factors influenced the emergence of sex-biased genetic patterns at global and local scales in the Roma population through time.

Patterns of genetic structure and adaptive positive selection in the Lithuanian population from high-density SNP data

The analysis of geographically specific regions and the characterization of fine-scale patterns of genetic diversity may facilitate a much better understanding of the microevolutionary processes affecting local human populations. Here we generated genome-wide high-density SNP genotype data in 425 individuals from six geographical regions in Lithuania and combined our dataset with available ancient and modern data to explore genetic population structure, ancestry components and signatures of natural positive selection in the Lithuanian population. Our results show that Lithuanians are a homogenous population, genetically differentiated from neighbouring populations but within the general expected European context. Moreover, we not only confirm that Lithuanians preserve one of the highest proportions of western, Scandinavian and eastern hunter-gather ancestry components found in European populations but also that of an steppe Early to Middle Bronze Age pastoralists, which together configure the genetic distinctiveness of the Lithuanian population. Finally, among the top signatures of positive selection detected in Lithuanians, we identified several candidate genes related with diet (PNLIP, PPARD), pigmentation (SLC24A5, TYRP1 and PPARD) and the immune response (BRD2, HLA-DOA, IL26 and IL22).

Phenotype comparison confirms ZMYND11 as a critical gene for 10p15.3 microdeletion syndrome

Proper epigenetic regulation processes are crucial in the normal development of the human brain. An ever-increasing group of neurodevelopmental disorders due to derangements of epigenetic regulation involve both microdeletion and monogenic syndromes. Some of these syndromes have overlapping clinical phenotypes due to haploinsufficiency-sensitive genes involved in microdeletions. It was shown recently that the ZMYND11 gene has important functions in epigenetic regulation as an unconventional transcription co-repressor of highly expressed genes, possibly acting in the repression of cryptic transcription from gene bodies. The aim of our study was to compare the clinical phenotypes of patients with 10p15.3 deletions with the phenotypes of patients with loss-of-function ZMYND11 mutations. The results of our study further confirm that the ZMYND11 gene is the critical gene for the clinical phenotype of 10p15.3 microdeletion involving the terminal ~4 Mb of chromosome 10p. In addition, accumulating clinical data allow for further characterisation of this syndrome, including neurodevelopmental disorder, characteristic dysmorphic features and some other more frequent symptoms, such as behavioural disturbances, hypotonia, seizures, low birth weight, short stature in those older than 10 years of age, genitourinary malformations and recurrent infections.

A novel intronic splice site tafazzin gene mutation detected prenatally in a family with Barth syndrome

Barth syndrome (BTHS) is a rare X-linked disease characterized by dilated cardiomyopathy, proximal skeletal myopathy and cyclic neutropenia. It is caused by various mutations in the tafazzin (TAZ) gene located on Xq28 that results in remodeling of cardiolipin and abnormalities in mitochondria stability and energy production. Here we report on a novel c.285-1G>C splice site mutation in intron 3 of the TAZ gene that was detected prenatally.

NSD1 duplication in Silver-Russell syndrome (SRS): molecular karyotyping in patients with SRS features

Silver-Russell syndrome (SRS) is a growth retardation syndrome characterized by intrauterine and postnatal growth retardation, relative macrocephaly and protruding forehead, body asymmetry and feeding difficulties. Nearly 50% of cases show a hypomethylation in 11p15.5, in 10% maternal uniparental disomy of chromosome 7 is present. A significant number of patients with SRS features also exhibit chromosomal aberrations. We analyzed 43 individuals referred for SRS genetic testing by molecular karyotyping. Pathogenic variants could be detected in five of them, including a NSD1 duplication in 5q35 and a 14q32 microdeletion. NSD1 deletions are detectable in overgrowth disorders (Sotos syndrome and Beckwith-Wiedemann syndrome), whereas NSD1 duplications are associated with growth retardation. The 14q32 deletion is typically associated with Temple syndrome (TS14), but the identification of a patient in our cohort reflects the clinical overlap between TS14 and SRS. As determination of molecular subtypes is the basis for a directed counseling and therapy, the identification of pathogenic variants in >10% of the total cohort of patients referred for SRS testing and in >16% of characteristic individuals with the characteristic SRS phenotype confirms the need to apply molecular karyotyping in this cohort.

CNV analysis in the Lithuanian population

Background

Although copy number variation (CNV) has received much attention, knowledge about the characteristics of CNVs such as occurrence rate and distribution in the genome between populations and within the same population is still insufficient. In this study, Illumina 770 K HumanOmniExpress-12 v1.0 (and v1.1) arrays were used to examine the diversity and distribution of CNVs in 286 unrelated individuals from the two main ethnolinguistic groups of the Lithuanian population (Aukštaičiai and Žemaičiai) (see Additional file 3). For primary data analysis, the Illumina GenomeStudio™ Genotyping Module v1.9 and two algorithms, cnvPartition 3.2.0 and QuantiSNP 2.0, were used to identify high-confidence CNVs.

Results

A total of 478 autosomal CNVs were detected by both algorithms, and those were clustered in 87 copy number variation regions (CNVRs), spanning ~12.5 Mb of the genome (see Table 1). At least 8.6 % of the CNVRs were unique and had not been reported in the Database of Genomic Variants. Most CNVRs (57.5 %) were rare, with a frequency of <1 %, whereas common CNVRs with at least 5 % frequency made up only 1.1 % of all CNVRs identified. About 49 % of non-singleton CNVRs were shared between Aukštaičiai and Žemaičiai, and the remaining CNVRs were specific to each group. Many of the CNVs detected (66 %) overlapped with known UCSC gene regions.

Conclusions

The ethnolinguistic groups of the Lithuanian population could not be differentiated based on CNV profiles, which may reflect their geographical proximity and suggest the homogeneity of the Lithuanian population. In addition, putative novel CNVs unique to the Lithuanian population were identified. The results of our study enhance the CNV map of the Lithuanian population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0373-6) contains supplementary material, which is available to authorized users.

Two new de novo interstitial duplications covering 2p14-p22.1: clinical and molecular analysis

We provide a detailed clinical and molecular analysis of 2 patients with de novo interstitial duplications at 2p14-p16.1 and 2p16.1-p22.1. The 10.13-Mb duplication of chromosome 2p14-p16.1 was identified in a 9-year-old boy with mental retardation, behavioral problems (hyperactivity, hyperphagia, and subsequent vomiting), recurrent respiratory tract infections, macrocephaly, epilepsy, and dysmorphic features. The 17.49-Mb duplication of 2p16.1-p22.1 was found in a 17-year-old girl with moderate mental retardation, behavioral and emotional problems, anxiety, and facial dysmorphic features. Very few cases of de novo interstitial duplication of 2p14-p22.1 are reported in the literature, with the great majority of them lacking a detailed molecular analysis. The abnormal phenotype of these cases is caused by mechanisms such as the overdose of a duplicated gene (or genes), the disruption of a gene or its regulatory sequence by the breakpoints of duplication, or by an excess of genetic material which may disorganize chromatin conformation affecting distant gene expression. The clinical and molecular analysis of these 2 rare de novo interstitial duplications provides useful information which is extremely valuable for clinical evaluation at the prenatal and postnatal level and for the molecular understanding of the underlying mechanisms of human diseases.

A novel de novo 1.8 Mb microdeletion of 17q21.33 associated with intellectual disability and dysmorphic features

We report on a de novo 17q21.33 microdeletion, 1.8 Mb in size, detected in a patient with mild intellectual disability, growth retardation, poor weight gain, microcephaly, long face, large beaked nose, thick lower lip, micrognathia and other dysmorphic features. The deletion was detected by whole-genome genotyping BeadChip assay and involves the genomic region between 45,682,246 and 47,544,816 bp on chromosome 17. Among the 24 RefSeq genes included in this deletion are the CA10 and CACNA1G genes that are involved in brain development and neurological processes. A possible candidate gene for the prenatal and postnatal growth retardation is the CHAD gene, which product chondroadherin is a cartilage protein with cell binding properties. These three genes may be responsible for the patient's phenotype.

Strategy for prenatal diagnosis of osteogenesis imperfecta by linkage analysis to the type I collagen loci COL1A1 and COL1A2

To improve prenatal diagnosis of osteogenesis imperfecta (OI) in Lithuania, possibilities of indirect molecular genetic diagnosis were investigated in 11 families with dominant OI. Segregation of polymorphic DNA markers closely linked to COL1A1 and COL1A2 genes with OI phenotype was investigated. Polymorphic DNA markers applied were individual haplotypes constructed using a set of restriction enzyme sites within or close to the genes. Comparison of phenotypic features with the concordant collagen locus showed that in four pedigrees with OI Sillence type I segregated with COL1A1, while two pedigrees with OI Sillence type I and OI type IV segregated with COL1A2. Out of six remaining pedigrees with OI Sillence type I, three were concordant at both loci, two pedigrees were discordant at the locus COL1A2 and non-informative at the locus COL1A1 and one pedigree was concordant at the locus COL1A1 and non-informative at the locus COL1A2. Informativity of DNA markers applied was also investigated in the Lithuanian OI families. The frequencies of six restriction enzyme site dimorphisms in type I collagen loci were estimated and polymorphism information content (PIC) values were calculated for each restriction site and for a combination of three sites. COL1A1 locus dimorphisms A/MspI, B/RsaI and F/MnlI, showed PIC values of 0.327, 0.191 and 0.366, respectively, giving a combined PIC of 0.656 at the locus, while COL1A2 locus dimorphisms C/EcoRI, D/MspI and E/RsaI RFLPs had PIC values of 0.357, 0.168 and 0.331, respectively, giving a combined PIC of 0.655 at the locus.