The research also looks into pathogenic variants for a number of human diseases. The results are formulated in
Table 1, showing the diseases with the highest prevalence: Stargardt disease caused by mutations in the
ABCA4 (MIM#601691) gene, which has also been previously reported
[7]. Researchers' results are concordant with earlier large-scale research into the incidences of pathogenic alleles associated with cystic fibrosis in a non-Finnish European population
[16]. Researchers' estimates of CF, phenylketonuria, and galactosemia prevalence were concordant with those of other genetic studies
[6][17].
Thus, researchers' results indicate the need to create genetic population databases for the interpretation of variants and the identification of disease risk factors.
WES allows for the identification of new gene variants in patients with MDs. Doctors Daniel Trujillano, Rami Abou Jamra, et al., using WES, sequenced 2819 samples of 1000 patients from 54 countries with a wide phenotypic spectrum. Overall, they determined 320 pathogenic (P) or likely pathogenic (LP) and 303 unique variants from 1000 patients undergoing clinical WES, 307 (30.7%) of which had a positive gene finding. In addition, other findings included ethylmalonic encephalopathy (ETHE1), Niemann–Pick disease type C2 (NPC2), Temtamy syndrome, pyruvate dehydrogenase E1-alpha deficiency (PDHA1), galactosemia (GALT), propionic acidemia (PCCA), homocystinuria (CBS), CF, long QT syndrome, and polycystic kidney disease. This justifies the idea that highly heterogeneous pathologies can be effectively detected using WES. Among other findings, new genes were detected, such as non-receptor protein tyrosine phosphatase type 23 (
PTPN23) associated with brain developmental delay and atrophy, potassium channel tetramerization domain containing 3 (
KCTD3) causing severe intellectual disability and seizures, alpha three subunit of sodium voltage-gated channel (
SCN3A) associated with autosomal dominant encephalopathy, protoporphyrinogen oxidase (
PPOX) causing variegate porphyria and developmental delay, and FERM and PDZ domain-containing 4 protein (
FRMPD4) implicated in X-linked intellectual disability as well as recessive Dravet syndrome. The total WES diagnostic rate stands at 31%
[18]. In another study, Joanne Trinh et al. sequenced 26,119 exome samples from 4351 patients with neurodevelopmental disorders (NDDs), such as global developmental and motor delay, macrocephaly, microcephaly, seizures, and delayed speech and language development. Researchers determined 65 rare variants in 14 genes. The 14 detected variants were classified as P or LP and included cyclin dependent kinase 13 (
CDK13), chromodomain helicase DNA binding protein 4 (
CHD4), potassium voltage-gated channel subfamily Q member 3 (
KCNQ3), lysine methyltransferase 5B (
KMT5B), transcription factor 20 (
TCF20), and C2H2-type zinc finger protein (
ZBTB18). The 51 remaining variants (78%) belonged to the VUS category. Two of the patients had multiple molecular diagnoses, including P/LP variants in forkhead box G1 transcription factor (FOXG1), CDK13, and the transmembrane protein 237 (
TMEM237) and
KMT5B genes. The total WES diagnostic rate was 31%
[19]. Zhang Q et al. sequenced 1360 patients to identify 604 genetic pathologies associated with 150 genetic syndromes, 510 genes, and 718 variants. In this cohort, the overall WES positive identification rate for disease-related gene alteration was 44.41%. Investigators detected growth abnormalities in 49.37% (118/239), seizures in 44.54% (102/229), autism spectrum disorder in 32.76% (38/116), global developmental delay in 54.84% (51/93), motor deterioration in 48.06% (99/206), abnormalities of the respiratory system in 40.61% (67/165), cerebral palsy in 41.26% (59/143), and abnormalities of the head or neck in 55.52% (161/290), the skin in 53.70 (58/108), the endocrine system in 49.78 (112/225), hearing or vision in 58.51% (55/94), the skeletal system in 53.95% (116/215), and the cardiovascular system in 43.20% (54/125) of samples
[20].
WES allows for the identification of new, very different variants in various populations. WES enabled us to identify new variants in the low-density lipoprotein receptor (
LDLR) gene in 59 Russian patients with a history of familial hypercholesterolemia (FH)
[21]. FH results from genetic variants in the
LDLR, apolipoprotein B (
APOB), and subtilisin/kexin proprotein convertase type 9 (
PCSK9) genes
[22]. FH-associated variants were determined in 25 children and 18 adults, showing mutation detection rates of 89 and 58% for the children and adults, respectively. In the adults, 13 patients had variants in the
LDLR gene, 3 patients had
APOB variants, and 2 had ATP-binding cassette transporter 5 (ABCG5)/G8 mutations. Twenty-one children had FH-associated variants in the
LDLR gene; see
Table 1. Researchers' study identified seven novel pathogenic or likely pathogenic
LDLR variants (
Table 2). Among them, four missense variants were located in the protein coding regions, and two were frameshift mutations responsible for the production of truncated proteins. These mutations were only reported in one patient, whereas an intron 6 splicing variant (c.940+1_c.940+4delGTGA) was detected in four unrelated individuals. Variant p.Gly592Glu in the
LDLR gene was identified in six (10%) Russian patients and may presumably constitute the main FH variant in the Russian population.