Uniparental disomy of multiple chromosomes in two cases with a complex phenotype.

Uniparental disomy (UPD) is the inheritance of both chromosomal homologs from one parent. Depending on the chromosome involved and the parental origin, UPD may result in phenotypic abnormalities due to aberrant methylation patterns or unmasking recessive conditions in isodisomic regions. UPD primarily originates from somatic rescue of a single meiotically-derived aneuploidy, most commonly a trisomy. Double UPD is exceedingly rare and triple UPD has not been previously described. Here, we report two unrelated clinical cases with UPD of multiple chromosomes; an 8-month-old male with maternal isodisomy of chromosome 7 and paternal isodisomy of chromosome 9, and a 4-week-old female with mixed paternal UPD for chromosomes 4, 10, and 14. These cases also demonstrate that although extremely rare, the detection of AOH on two or more chromosomes may warrant additional clinical and laboratory investigation such as methylation and STR marker analysis, especially when involving chromosomes known to be associated with imprinting disorders.

Identification of sex-specific genetic associations in response to opioid analgesics in a White, non-Hispanic cohort from Southeast Minnesota.

The study of sex-specific genetic associations with opioid response may improve the understanding of inter-individual variability in pain treatments. We investigated sex-specific associations between genetic variation and opioid response. We identified participants in the RIGHT Study prescribed codeine, tramadol, hydrocodone, and oxycodone between 01/01/2005 and 12/31/2017. Prescriptions were collapsed into codeine/tramadol and hydrocodone/oxycodone. Outcomes included poor pain control and adverse reactions within six weeks after prescription date. We performed gene-level and single-variant association analyses stratified by sex. We included 7169 non-Hispanic white participants and a total of 1940 common and low-frequency variants (MAF > 0.01). Common variants in MACROD2 (rs76026520), CYP1B1 (rs1056837, rs1056836), and CYP2D6 (rs35742686) were associated with outcomes. At the gene level, FAAH, SCN1A, and TYMS had associations for men and women, and NAT2, CYP3A4, CYP1A2, and SLC22A2 had associations for men only. Our findings highlight the importance of considering sex in association studies on opioid response.

Targeted Genotyping in Clinical Pharmacogenomics: What Is Missing?

Clinical pharmacogenomic testing typically uses targeted genotyping, which only detects variants included in the test design and may vary among laboratories. To evaluate the potential patient impact of genotyping compared with sequencing, which can detect common and rare variants, an in silico targeted genotyping panel was developed based on the variants most commonly included in clinical tests and applied to a cohort of 10,030 participants who underwent sequencing for CYP1A2, CYP2C19, CYP2C9, CYP2D6, CYP3A4, CYP3A5, DPYD, SLCO1B1, TPMT, UGT1A1, and VKORC1. The results of in silico targeted genotyping were compared with the clinically reported sequencing results. Of the 10,030 participants, 2780 (28%) had at least one potentially clinically relevant variant/allele identified by sequencing that would not have been detected in a standard targeted genotyping panel. The genes with the largest number of participants with variants only detected by sequencing were SLCO1B1, DPYD, and CYP2D6, which affected 13%, 6.3%, and 3.5% of participants, respectively. DPYD (112 variants) and CYP2D6 (103 variants) had the largest number of unique variants detected only by sequencing. Although targeted genotyping detects most clinically significant pharmacogenomic variants, sequencing-based approaches are necessary to detect rare variants that collectively affect many patients. However, efforts to establish pharmacogenomic variant classification systems and nomenclature to accommodate rare variants will be required to adopt sequencing-based pharmacogenomics.

Most noninvasive prenatal screens failing due to inadequate fetal cell free DNA are negative for trisomy when repeated.

OBJECTIVE: We aimed to test for an association between the amount of circulating fetal cell-free DNA and trisomy, and whether NIPS failure due to low fetal fraction indicates trisomy risk. METHOD: Maternal BMI, maternal age, fetal sex, gestational age, fetal cfDNA fraction, and NIPS results was collected on 2374 pregnancies. Additional clinical information was available for 1180 research consented patients. We investigated associations between fetal fraction and available variables and determined the success rate of repeat NIPS testing. RESULTS: Fetal trisomy was marginally associated with decreased fetal fraction (P = .067). However, the proportions of trisomy events were not significantly increased in women who had failed NIPS due to low fetal fraction (<4%) (OR = 1.37 [0.3-7.4]; P = .714). 66% of repeated NIPS after a second blood draw were successful. CONCLUSION: Failure to meet the clinical cutoff of 4% fetal fraction established for NIPS accuracy did not suggest increased risk for trisomy in our cohort. Because repeat testing was successful in the majority of cases and most failures were explained by high BMI and low gestational age, a redraw may be an appropriate next step before invasive screening due to concerns for trisomic pregnancies.

Characterizing false-positive fluorescence in situ hybridization results by mate-pair sequencing in a patient with chronic myeloid leukemia and progression to myeloid blast crisis.

Traditional cytogenetic testing methodologies, including conventional chromosome analysis and fluorescence in situ hybridization (FISH), are invaluable for the detection or recurrent genetic abnormalities in various hematologic malignancies. However, technological advances, including a novel next-generation sequencing technique termed mate-pair sequencing (MPseq), continue to revolutionize the field of cytogenetics by enabling the characterization of structural variants at a significantly higher resolution compared to traditional methodologies. To illustrate the power of MPseq, we present a 27-year-old male diagnosed with chronic myeloid leukemia in myeloid blast crisis with multiple chromosomal abnormalities observed in all 20 metaphases from a peripheral blood specimen, including t(9;22)(q34;q11.2) and t(4;11)(q12;p15). Suspicious of a novel NUP98/PDGFRA fusion [t(4;11)(q12;p15)], break-apart FISH probe sets for the PDGFRA (4q12) and NUP98 (11p15.4) gene regions were performed and were both positive in approximately 86% of 200 interphase nuclei. However, subsequent MPseq testing revealed breakpoints located within the NUP98 gene and within an intergenic region (4q12) located between the CHIC2 and PDGFRA genes, indicating this 4;11 translocation does not result in the predicted NUP98/PDGFRA gene fusion as inferred from FISH and conventional chromosome results. This case demonstrates the clinical utility of MPseq, particularly for characterizing novel gene fusion events which may ultimately identify a false-positive FISH result.

FANCM, RAD1, CHEK1 and TP53I3 act as BRCA-like tumor suppressors and are mutated in hereditary ovarian cancer.

Although 25% of ovarian cancer cases are due to inherited factors, most of the genetic risk remains unexplained. We previously identified candidate genes through germline whole exome sequencing of BRCA1/BRCA2 negative ovarian cancer patients with familial risk. Here, we performed functional assessment to determine whether they act as BRCA-like tumor suppressors. Seven candidate risk genes were targeted by siRNA for mRNA depletion followed by functional assays for clonogenic survival, cytotoxicity to DNA damaging agents, and involvement in homologous recombination repair. BRCA1 and BRCA1 were targeted as standards for loss of function outcome. Knockdown of various candidate genes led to tumor suppressor phenotypes also observed in BRCA1/BRCA2 deficient cells. Deficiency of CHEK1, FANCM and TP53I3 led to reduced homologous recombination repair efficiency. Knockdown of RAD1, CHEK1 or FANCM led to a decrease in cellular viability and cells deficient in CHEK1, RAD1 or TP53I3 displayed increased sensitivity to cisplatin. Functional studies of candidate genes identified by whole exome sequencing complements bioinformatics techniques and aid the implication of novel risk loci. The results of this study suggest that genes found mutated in hereditary ovarian cancer, FANCM, RAD1, CHEK1 and TP53I3, act as BRCA-like tumor suppressors.