Study techniques

 

Exome sequencing

NGS service based on sequencing the coding portion of the human genome. It is a versatile tool that enables the simultaneous testing of a large amount of genes, and it is particularly useful in those cases where clinical presentation does not allow selecting a specific clinical panel or in pathologies with a very wide range of candidate genes, e.g. epilepsy. The exome service allows for TARGETED (predefined) testing of a group of candidate genes or for CLINICAL (open) analysis, where an ad hoc test is performed based on the clinical features of each particular case. The most complex cases may benefit from TRIO- or FAMILY-BASED exome testing, which jointly analyze the exomes of several family members, taking into account the status of each studied individual (affected or healthy) and the suspected inheritance pattern.

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Gene sequencing

Individual gene sequencing and interpretation service. Depending on its size and on the regions of interest, we can offer an approach based on Sanger sequencing or on NGS (enrichment using amplicons or hybridization probes). The NGS-based approach allows detecting copy number variations (CNVs).

NextGenDx® massive sequencing (NGS)

Next Generation Sequencing (NGS), or massive sequencing, is a term used to describe a group of newly developed technologies able to perform massive DNA sequencing. This means that millions of small DNA fragments can be sequenced at once, generating a vast amount of data. These data can add up to gigabytes of information, equivalent to 1,000 millions of DNA base pairs. In comparison, formerly used methods could only sequence one DNA fragment at a time, generating between 500 and 1,000 DNA base pairs in a single reaction.

NextGenDx® is indicated when a specific group of genes needs to be analyzed at the highest levels of diagnostic accuracy. It is aimed at:

• Monogenic diseases or diseases associated with a small number or large genes.
• Multigenic or genetically heterogeneous diseases with complex differential diagnosis.

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Expansions

DNA fragment analysis service for pathologies caused by nucleotide expansions. Specific approaches for each disease allow distinguishing between pathologic and non-pathologic alleles.

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MLPA testing

(Multiplex Ligation-dependent Probe Amplification)
Semiquantitative technique that is widely applied in molecular genetic laboratories and that allows diagnosing pathologies caused by copy number variations and, in some cases, by alterations in DNA methylation. A wide variety of commercial kits are available to test individual genes, gene panels related to specific pathologies, or large chromosomal regions involved in microdeletion/microduplication syndromes. HIC offers MLPA services based on MRC-Holland kits.

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Real Time PCR

It consists of a PCR analysis that allows amplifying and simultaneously quantifying the product of said PCR. To do this, it is based on the fundamentals of conventional PCR, but uses a fluorophore that will allow the amount of amplification to be measured in real time.

SNP Array

They include more than 290 microdeletion/microduplication syndromes.

Array analysis allows detecting copy number gains or losses throughout the whole genetic material of the patient. Within the field of cardiology, it is considered a first-line test for patients with congenital heart disease associated with other malformations, particularly intellectual disability, autism spectrum disorders, and/or multiple congenital malformations. Among its advantages are the possibility of testing DNA from virtually any tissue, including non-cultured tissue; the detection of citogenetic abnormalities that cannot be detected by conventional tests; the identification of breakage points in chromosomal rearrangements, and the detection of loss of heterozygosity.

Array CGH

It is also known as molecular karyotyping, and its main advantage over classic karyotyping is its high sensitivity, which allows detecting structural variants that go unnoticed in conventional karyotyping. CGH array technology allows detecting losses and gains of genetic material and unbalanced rearrangements throughout the whole genome of an individual.

Postnatal CGX 108K is specifically designed for genetic diagnosis. Its mean resolution is 100 kb over the whole genome, and high resolution is 20 kb for regions of interest of the genome (regions with direct association between copy number variations and a described pathology or syndrome).

Array 37K is specifically designed for prenatal diagnosis and allows detecting genetic and chromosomal alterations with a single test. Its resolution is 10 times greater than that of conventional karyotyping and 50 times greater in critical regions for the main syndromes. Without substantially decreasing resolution in regions of interest, CGX 37K shows low coverage levels in the rest of the genome in order to minimize diagnostic uncertainty.

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Sanger

Sanger sequencing is considered the gold standard technique for the identification of point mutations and small INDELs. It consists of the analysis of the entire coding sequence of a specific gene. The design that Imegen carries out for this type of study allows the analysis of the sequence of all the coding regions (exons) of each gene, taking into account all the relevant transcripts described in the databases. The study also includes the intronic regions adjacent to each exon, as well as 5′ and 3′ regions, with the intention of identifying variations in regulatory or processing regions.