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Natālija Proņina and Rita Lugovska

Association between minihaplotypes and mutations at the phenylalanine hydroxylase locus in Latvian phenylketonuria patients

Phenylketonuria (PKU) is an inherited metabolic disease caused by recessively inherited mutations in the PAH gene that encodes the enzyme phenylalanine hydroxylase (PAH). Altogether, 20 diseases causing mutations were identified in Latvian PKU patients. R408W, the most common mutation, accounted for 73% of Latvian PKU chromosomes and was mostly observed in association with the VNTR3/STR238 minihaplotype. Minihaplotypes also were established for the other 19 mutations and one unknown PKU chromosome. Mutation E280K was almost exclusively associated with minihaplotype 9/250, and mutation IVS10-11G>A was strongly associated with the VNTR7/STR250 minihaplotype and was possibly of Mediterranean origin. It was found that minihaplotypes can be useful in studies concerning the origin and distribution of PAH mutations in human populations and for analysis of rare mutations in PAH gene and for prenatal diagnosis.

Open access

Olga Šterna, Natālija Proņina, Ieva Grīnfelde, Sandra Kušķe, Astrīda Krūmiņa, Rita Lugovska and Aigars Pētersons

Spectrum and Frequency of the GJB2 Gene Mutations Among Latvian Patients with Prelingual Nonsyndromic Hearing Loss

Mutations in the GJB2 gene (connexin 26) are the most common cause of congenital nonsyndromic severe-to-profound hearing loss. Sixty-five hearing impaired probands from Latvia were tested for mutations in the GJB2 gene to determine the percentage of hearing loss attributed to connexin 26 and the types of mutations in this population. A total of 62% of patients tested had GJB2 mutations. Four different mutations in the GJB2 gene were identified in Latvian patients with nonsyndromic sensorineural hearing loss: 35delG, 311-324del14, 235delC and M34T. The most prevalent mutation is 35delG (47% of all probands were homozygous and 8% compound heterozygous). Our findings support the conclusion that the 35delG mutation is the most prevalent GJB2 mutation and that it is the common cause of hereditary nonsyndromic hearing loss in populations of European descent.

Open access

Zanda Daneberga, Zita Krūmiņa, Baiba Lāce, Daiga Bauze, Natālija Proņina and Rita Lugovska

Fragile X Syndrome in Mentally Retarded Patients from Latvia

The aim of this study was to estimate the prevalence of FXS in Latvia and characterise the FMR1 CGG-repeat structure in Latvian patients exhibiting mental retardation. A group of 352 unrelated patients with mental retardation (MR) referred from clinical geneticists was screened by PCR for the normal allele. In a sample of 245 chromosomes the CGG repeat number was determined by Applied Biosystems protocol on ABI Prism 310. Prevalence of 29, 30, and 31 CGG repeats was found for the normal allele. Five affected patients were detected (detection rate 2.56%). AGG interspersion pattern analysis showed stability of transmission to the next generation for 12 intermediate alleles. The found detection rate of FXS in our survey among MR patients was similar to the detection rate reported in literature. Taking into account the number of confirmed FXS cases we suggest that FXS is still clinically unrecognized in paediatrician practice.

Open access

Tālis Kauliñš, Natālija Proñina, Henrik Rüffert, Markus Wehner, Māris Mihelsons, Oksana Osipova and Aleksejs Miščuks

Identification of A Novel Mutation in RYR1 Gene in Malignant Hyperthermia-Like Patient's Family Members

Malignant hyperthermia (MH) is a rare pharmacogenetic disorder with an autosomal dominant inheritance that presents as a hypermetabolic response in skeletal muscle to volatile anaesthetic (halothane, isoflurane, desflurane, sevoflurane) and the depolarising muscle relaxant succinil-choline and rarely to stresses such as vigorous exercise and heat. We investigated the relatives of an individual with suspected MH and found a novel mutation in RYR1 gene. The molecular analysis of RYR1 gene revealed a novel nucleotide substitution in exon 6 - G528T (Glu-176-Asp) in four family members of the patient. The in vitro contracture test (IVCT) according to the European Malignant Hyperthermia Group (EMHG) guidelines showed a MH susceptible phenotype in two tested family members.