PIGN-Related Disease in Two Lithuanian Families: A Report of Two Novel Pathogenic Variants, Molecular and Clinical Characterisation.

Background and Objectives: Pathogenic variants of PIGN are a known cause of multiple congenital anomalies-hypotonia-seizures syndrome 1 (MCAHS1). Many affected individuals have clinical features overlapping with Fryns syndrome and are mainly characterised by developmental delay, congenital anomalies, hypotonia, seizures, and specific minor facial anomalies. This study investigates the clinical and molecular data of three individuals from two unrelated families, the clinical features of which were consistent with a diagnosis of MCAHS1. Materials and Methods: Next-generation sequencing (NGS) technology was used to identify the changes in the DNA sequence. Sanger sequencing of gDNA of probands and their parents was used for validation and segregation analysis. Bioinformatics tools were used to investigate the consequences of pathogenic or likely pathogenic PIGN variants at the protein sequence and structure level. Results: The analysis of NGS data and segregation analysis revealed a compound heterozygous NM_176787.5:c.[1942G>T];[1247_1251del] PIGN genotype in family 1 and NG_033144.1(NM_176787.5):c.[932T>G];[1674+1G>C] PIGN genotype in family 2. In silico, c.1942G>T (p.(Glu648Ter)), c.1247_1251del (p.(Glu416GlyfsTer22)), and c.1674+1G>C (p.(Glu525AspfsTer68)) variants are predicted to result in a premature termination codon that leads to truncated and functionally disrupted protein causing the phenotype of MCAHS1 in the affected individuals. Conclusions: PIGN-related disease represents a wide spectrum of phenotypic features, making clinical diagnosis inaccurate and complicated. The genetic testing of every individual with this phenotype provides new insights into the origin and development of the disease.

Pathogenic homozygous variant in POMK gene is the cause of prenatally detected severe ventriculomegaly in two Lithuanian families.

Biallelic pathogenic variants in POMK gene are associated with two types of dystroglycanopathies: limb-girdle muscular dystrophy-dystroglycanopathy, type C12 (MDDGC12), and congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies, type A12 (MDDGA12). These disorders are very rare and have been previously reported in 10 affected individuals. We present two unrelated Lithuanian families with prenatally detected hydrocephalus due to a homozygous nonsense variant in the POMK. The first signs of hydrocephalus in the affected fetuses became evident at 15 weeks of gestation and rapidly progressed, thus these clinical features are compatible with a diagnosis of MDDGA12. The association between pathogenic POMK variants and macrocephaly and severe hydrocephalus has been previously reported only in two families. Clinical and molecular findings presented in this report highlight congenital hydrocephalus as a distinct feature of POMK related disorders and a differentiator from other dystroglycanopathies. These findings further extend the spectrum of MDDGA12 syndrome.

Cell-Free DNA Analysis of Targeted Genomic Regions in Maternal Plasma for Non-Invasive Prenatal Testing of Trisomy 21, Trisomy 18, Trisomy 13, and Fetal Sex.

BACKGROUND: There is great need for the development of highly accurate cost effective technologies that could facilitate the widespread adoption of noninvasive prenatal testing (NIPT). METHODS: We developed an assay based on the targeted analysis of cell-free DNA for the detection of fetal aneuploidies of chromosomes 21, 18, and 13. This method enabled the capture and analysis of selected genomic regions of interest. An advanced fetal fraction estimation and aneuploidy determination algorithm was also developed. This assay allowed for accurate counting and assessment of chromosomal regions of interest. The analytical performance of the assay was evaluated in a blind study of 631 samples derived from pregnancies of at least 10 weeks of gestation that had also undergone invasive testing. RESULTS: Our blind study exhibited 100% diagnostic sensitivity and specificity and correctly classified 52/52 (95% CI, 93.2%-100%) cases of trisomy 21, 16/16 (95% CI, 79.4%-100%) cases of trisomy 18, 5/5 (95% CI, 47.8%-100%) cases of trisomy 13, and 538/538 (95% CI, 99.3%-100%) normal cases. The test also correctly identified fetal sex in all cases (95% CI, 99.4%-100%). One sample failed prespecified assay quality control criteria, and 19 samples were nonreportable because of low fetal fraction. CONCLUSIONS: The extent to which free fetal DNA testing can be applied as a universal screening tool for trisomy 21, 18, and 13 depends mainly on assay accuracy and cost. Cell-free DNA analysis of targeted genomic regions in maternal plasma enables accurate and cost-effective noninvasive fetal aneuploidy detection, which is critical for widespread adoption of NIPT.

A novel missense mutation in the NSDHL gene identified in a Lithuanian family by targeted next-generation sequencing causes CK syndrome.

The NSDHL gene encodes 3ß-hydroxysteroid dehydrogenase involved in one of the later steps of the cholesterol biosynthetic pathway. Mutations in this gene can cause CHILD syndrome (OMIM 308050) and CK syndrome (OMIM 300831). CHILD syndrome is an X-linked dominant, male lethal disorder caused by mutations in the NSDHL gene that result in the loss of the function of the NSDHL protein. CK syndrome is an allelic X-linked recessive disorder. So far, 13 patients with CK syndrome from two families have been reported on. We present a new five-generation family with affected males manifesting clinical features of CK syndrome. Next generation sequencing was targeted to a custom panel of 542 genes with known or putative implication on intellectual disability. Missense mutation p.Gly152Asp was identified in the NSDHL gene in the DNA sample of the affected male. Mutation carrier status was confirmed for all the obligate carriers in the family. The clinical features of the affected males in the family manifested as weak fetal movements, severe intellectual disability, seizures, spasticity, atrophy of optic discs, microcephaly, plagiocephaly, skeletal abnormalities, and minor facial anomalies, including a high nasal bridge, strabismus, and micrognathia. A highly significant preferential transmission of the mutation was observed in this and previous families segregating CK syndrome. Our report expands the clinical spectrum of this syndrome to include weak fetal movements, spasticity, and plagiocephaly, and transmission ratio distortion. The various findings in these patients increase our understanding of the diversity of the clinical presentation of cholesterol biosynthesis disorders.

Recurrent fetal syndromic spina bifida associated with 3q26.1-qter duplication and 5p13.33-pter deletion due to familial balanced rearrangement.

OBJECTIVE: Neural tube defects belong to the second most common group of congenital anomalies, after heart defects, which can be diagnosed by prenatal ultrasonography. Rarely, neural tube defects can be associated with chromosomal abnormalities, including full and partial aneuploidies. We report a familial fetal case with syndromic spina bifida and discuss its association with partial 3q duplication and partial 5p deletion. MATERIALS AND METHODS: Clinical findings of three affected family members in two generations and two carriers of the balanced translocation are described. Conventional cytogenetic and fluorescence in situ hybridization (FISH) analysis of the carrier, as well as subtelomeric multiplex ligation-dependent probe amplification (MLPA) and array comparative genomic hybridization (CGH) analysis on the DNA extracted from affected family members was performed. RESULTS: Subtelomeric FISH analysis of the proposita revealed balanced reciprocal translocation between the long arm of chromosome 3 and short arm of chromosome 5. Subtelomeric MLPA screening of the first child revealed the deletion in 5p15.33 and duplication in 3q29 chromosomal loci, the finding consisting of the unbalanced rearrangement involving the short arm of chromosome 5 and long arm of chromosome 3. Array CGH analysis of the DNA of the second affected child revealed a 31.1Mb duplication of 3q26.1-qter and a 33.6Mb deletion of 5p13.33-pter. CONCLUSION: Our report serves to emphasize the consistency in the prenatal sonographic feature of spina bifida in consecutive pregnancies with fetuses associated with partial trisomy 3q (3q26.1-qter) and partial monosomy 5p (5p13.33-pter). The use of molecular cytogenetic technologies such as array CGH and FISH is important for clarifying any type of unbalanced chromosome rearrangement.

COL1A1 mutation analysis in Lithuanian patients with osteogenesis imperfecta.

Osteogenesis imperfecta (OI) is a generalised disorder of connective tissue characterised by an increased fragility of bones and also manifested in other tissues containing collagen type I, by blue sclera, hearing loss, dentinogenesis imperfecta, hyperextensible joints, hernias and easy bruising. OI is dominantly inherited and results in >90% OI cases, caused by mutations in one of the two genes COL1A1 or COL1A2 coding for type I procollagen. The Lithuanian OI database comprises 147 case records covering the period of 1980 - 2001. Clinical and genealogical analysis of OI cases/families from Lithuania available for examination revealed 18 familial cases of OI type I and 22 sporadic cases: OI type II (3 cases), OI type III (11 cases) and OI type I (8 cases). As a result of their molecular genetic investigation, 11 mutations were identified in the COL1A1 gene in 13 unrelated patients. Of them, nine mutations (E500X, G481A, c.2046insCTCTCTAG, c.1668delT, c.1667insC, c.4337insC, IVS19+1G > A, IVS20-2A > G, IVS22-1G > T) appeared to be novel, i.e. not yet registered in the Human Type I and Type III Collagen Mutations Database (http://www.le.ac.uk/genetics/collagen).