Molecular genetic analyses

Genechron offers molecular services to support the diagnosis of hereditary pathologies, designs and synthesizes specific primers for the amplification and sequencing of target genes and optimizes the amplification and sequencing conditions. The service includes the complete analysis of the coding regions and the mutational analysis of the following genes: CFTR, HBB, GJB2, SMN1.

Furthermore, an analysis service is also offered on the FMR1 gene (Fragile X syndrome) and on the regions of the Y chromosome linked to male infertility.

Peripheral blood karyotyping is a Classical Cytogenetic analysis through which it is possible to analyze the number and shape of the chromosomes present in a eukaryotic cell. Karyotype analysis is the ordered representation of an individual’s chromosomal complement, according to a standardized scheme. Karyotype analysis involves taking a blood sample (2-3 ml), setting up a cell culture and subsequent treatment to fix the chromosomes on a slide. The chromosomes are colored, observed and analyzed in number and morphology to highlight, or exclude, alterations compared to the species standard.

Unlike other genetic analyses that can be performed on any organic material containing DNA, karyotypic analyzes can only be performed on live cells capable of replicating. The substrate used in karyological analyses is therefore peripheral blood. When the structure and/or number of chromosomes changes without loss or increase of genetic material, there is no effect on the cells and therefore no pathologies occur for the subject in question. Only in the development of mature oocytes or spermatozoa could unbalanced oocytes or spermatozoa appear which, if involved in fertilization, lead to a germ line with an unbalanced chromosomal heritage. This leads to the impossibility of continuing the pregnancy after fertilization or at a later stage of the embryo’s development will lead to a miscarriage or even the birth of a child with malformations.

Cystic Fibrosis is an autosomal recessive disease caused by mutations in the CFTR (Cystic Fibrosis Transmembrane conductance Regulator) gene. About 2000 mutations are known of the CFTR gene which codes for a protein localized on the apical membrane of the epithelial cells that line the ducts and cavities of many organs in our body. This protein constitutes an ion channel for the passage of chlorine and other electrolytes towards the outside with consequent secretion of water.

Mutations in the CFTR gene (about 80 have been identified) disrupt the function of the chloride channel, causing the production of mucus in the cells of the male genital tract. This mucus blocks the tubes that carry sperm from the testes (the deferens) while they are forming, causing them to deteriorate before birth. Although the testes usually develop and function normally, sperm cannot be transported through the vas deferens, as a result, men with this condition are unable to father (infertile) children unless they use assisted reproductive technologies.

Hereditary thrombophilia is the genetic predisposition of a person to develop thrombotic episodes during life. In pregnancy, hereditary thrombophilia can increase the risk of spontaneous abortion or intrauterine fetal death due to thrombosis of the placental vessels. The genetic defects responsible for susceptibility to hereditary thrombophilia are caused by genes such as ACE, AGT, Factor II, Cambridge Factor V, Leiden Factor V, Factor XIII and MTHFR. The main mutations affecting these genes are identified by real-time PCR and, in some specific cases, by sequencing.

Hearing loss is a very frequent and extremely heterogeneous disease. In the general population its prevalence increases with age: 0.1% of children have hearing problems as do 4% of adults and 10% of the population over the age of 60. In Western countries, 60% of deafness cases are linked to genetic factors and 40% to environmental causes such as infections during pregnancy, trauma, use of ototoxic drugs or other pathologies. Non-syndromic hereditary forms of deafness present with wide genetic heterogeneity and different modes of transmission. The most widespread forms of hereditary deafness (around 80%) have an autosomal recessive mode of transmission and are largely due to mutations in the GJB2 gene, which codes for connexin 26 (cx26), a protein of the Organ of Corti. The genetic test consists of analyzing the sequence of the GJB2 gene to identify the presence of mutations.

Thalassemias are hereditary pathologies due to alterations in the synthesis of the components of hemoglobin whose function is to capture oxygen from the lungs and transport it to the various tissues, and to collect the carbon dioxide produced in the tissues and then transport it to the lungs, where is eliminated. The HBB gene codes for a protein called beta-globin which constitutes one of the subunits of hemoglobin. Mutations in the HBB gene cause deficiency or absence of the synthesis of the beta chains of hemoglobin and are therefore responsible for the onset of beta thalassemia also known as Mediterranean Anemia or erythroblastic anemia, the incidence of which at birth (for the severe form) is estimated at 100,000 /year. Transmission is autosomal recessive and approximately 400 mutations have been identified.

Spinal muscular atrophy is a disease characterized by degeneration of the motor neurons of the anterior horns of the spinal cord resulting in atrophy and weakness of the muscles of the trunk and limbs. It is possible to divide SMA into three clinical types according to the age of onset, the degree of muscle impairment and the age of death. In clinical reality, many patients present a severity of the disease that creates a continuum between the severe and mild forms which seem to blend into each other. The gene responsible for SMA was called SMN1 which means motor neuron survival gene. This gene is located on chromosome 5 in the 5q13 region where there is also a gene almost identical to SMN1 which is called SMN2.
SMA is caused by absence or alteration of the SMN1 gene due to deletion (lack), conversion of SMN1 to SMN2, or in rare cases (less than 4%), small mutations. Molecular analysis therefore allows a rapid and early diagnosis.

Fragile X Syndrome occurs in both males and females and symptoms present more prominently in males. The incidence is estimated at 1 case in 4000 males and 1 in 7000 females. The Syndrome is caused by the expansion of a CGG trinucleotide repeat (triplet) within the FMR1 gene (Fragile (FXS). Some people have a number of intermediate repeats within the FMR1 gene (50 to 200) that cause no effect. This intermediate alteration is called pre-mutation, and individuals who possess it are healthy carriers, because in subsequent generations the repetitions can increase causing the complete mutation. Molecular analysis allows the determination of the number of repeats of nucleotide triplets (genotyping) and can be used for prenatal and pre-implantation diagnosis.

 

Male sterility due to microdeletions of the Y chromosome is characterized by severe deficits in spermatogenesis. The estimated prevalence is 1/2,500. The mode of transmission is linked to the Y chromosome, with incomplete penetrance, but, since deletions are often associated with infertility, they usually originate de novo. 5-10% of cases of azospermia (absence of sperm) or severe secretory oligospermia (<1 million sperm/ml of seminal fluid) are associated with microdeletions in the euchromatic portion of the long arm of the Y chromosome, in the AZF locus (Azospermia Factor).

 

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