Comparative study of three PCR-based copy number variant approaches, CFMSA, M-PCR, and MLPA, in 22q11.2 deletion syndrome

Techniques, procedures, and applications in host genetic analysis

This chapter overviews genetic techniques' fundamentals and methodological features, including different approaches, analyses, and applications that have contributed to advancing health and disease. The aim is to describe laboratory methodologies and analyses employed to understand the genetic landscape of different biological contexts, from conventional techniques to cutting-edge technologies. Besides describing detailed aspects of the polymerase chain reaction (PCR) and derived types as one of the principles for many novel techniques, we also discuss microarray analysis, next-generation sequencing, and genome editing technologies such as transcription activator-like effector nucleases (TALENs) and the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) systems. These techniques study several phenotypes, ranging from autoimmune disorders to viral diseases. The significance of integrating diverse genetic methodologies and tools to understand host genetics comprehensively and addressing the ethical, legal, and social implications (ELSI) associated with using genetic information is highlighted. Overall, the methods, procedures, and applications in host genetic analysis provided in this chapter furnish researchers and practitioners with a roadmap for navigating the dynamic landscape of host-genome interactions.

Genetics and public health: the experience of a reference center for diagnosis of 22q11.2 deletion in Brazil and suggestions for implementing genetic testing

Considering the prevalence of 22q11.2 deletion syndrome (22q11.2 DS) of around 1:4,000 and of palatal abnormalities in 70 % of the cases of 22q11.2 DS and taking into account the Brazilian health system and its current situation of medical genetic services, this study aims to contribute to establish strategies for genetic diagnosis. The access to genetic testing at 11 services was investigated and samples from 100 patients with palatal abnormalities and suspicion of 22q11.2 DS were sent to a reference center. Laboratorial techniques included karyotyping, fluorescence in situ hybridization (FISH), and multiplex ligation-dependent probe amplification. Costs were also calculated. Disparities among centers for genetic diagnosis were evident, with remarkable regional differences. Some of the obstacles encountered were difficulties for families to show up for medical appointments, complementary evaluations, and for the clinics to send the samples to the reference center. A conclusive diagnosis was reached for 38 % of patients. Combination of karyotyping and FISH had better laboratorial cost-effectiveness. These results might represent the reality for the investigation of other genetic conditions. Clinical and laboratorial approaches herein presented could be adapted for use under different genetic conditions in the Brazilian health system, which has relatively limited financial and human resources. Suggestions for the rational implementation of genetic testing in developing countries are presented.

MLPA: a prenatal diagnostic tool for the study of congenital heart defects?

Congenital heart defects (CHD) represent the most common birth defects, so they are not a rare finding when performing routine ultrasound examinations during pregnancy. Once chromosome abnormalities have been excluded in a fetus with a CHD, chromosome 22q11.2 deletion is usually investigated by FISH, as it is the most frequent microdeletion syndrome and is generally associated with cardiac malformations. If 22q11.2 microdeletion is ruled out, the etiology of the CHD remains generally unexplained, making familial genetic counseling difficult. To evaluate the usefulness of Multiplex Ligation-dependent Probe Amplification (MLPA) kits designed for the study of 22q11.2 and other genomic regions previously associated with syndromic CHD, we performed MLPA in 55 pregnancies with fetuses presenting CHD, normal karyotype and negative FISH results for 22q11.2 microdeletion, which constitutes the largest prenatal series reported. Definitive MLPA results were obtained in 50 pregnancies, and in this setting such MLPA kits did not detect any imbalance. On the other hand, to compare FISH and MLPA techniques for the study of 22q11.2 microdeletions, we performed MLPA in 4 pregnancies known to have 22q11.2 deletions (by FISH). All four 22q11.2 microdeletions were also detected by MLPA, which corroborates that it is a reliable technique for the diagnosis and characterization of 22q11.2 deletions. Finally, we evaluated the possibility of replacing conventional FISH by MLPA for the prenatal diagnosis of CHD, comparing the diagnostic potential, results delivery times, repetition and failure rates and cost of both techniques, and concluded that FISH should still be the technique of choice for the prenatal diagnosis of fetuses with CHD.