Placental Molar Disease: What are the Benefits and Barriers to the Adoption of a Comprehensive Diagnostic Service?

The molecular cytogenetic analysis of specimens (genotyping) suspicious for hydatidiform mole (HM) significantly improves diagnostic accuracy over histopathology and immunohistochemical analysis alone, particularly in the classification of partial mole. However, the implementation of this advance in diagnostics has been slow. This study sought to identify the major benefit and potential barriers to the adoption of genotyping. A pilot Placental Molar Diagnostic (PMD) Service was established combining histopathology, p57 immunohistochemistry, and molecular genotyping analysis for both in-house and referred-in cases suspicious for HM or with a preliminary diagnosis of HM. A retrospective analysis of 117 cases received in the first 16 mo was conducted to identify the utility of the PMD Service and factors or barriers which precluded optimal results. A final diagnosis of HM was made in 73 cases (37 complete HMs and 36 partial HMs). The remaining 44 cases were hydropic abortuses. Three potential barriers were identified that could lead to less than optimal results from a PMD Service: prevalence of noninformative genotyping, lack of any available or appropriate paraffin blocks, and inappropriate deferral of genotyping. The major utility of this pilot PMD Service was to increase the specificity of a diagnosis of HM, and avoid unnecessary clinical follow-up in 37% of cases with an initial suspicion or diagnosis of HM. Measures can be undertaken to address potential barriers to the implementation of a comprehensive placental diagnostic platform. Underutilization of molecular genotyping in the diagnosis of HM likely leads to inappropriate management and "downstream" costs in a significant proportion of patients suspected of having HM.

PGD for a carrier of an intrachromosomal insertion using aCGH.

Intrachromosomal insertions are rare and difficult to diagnose. However, making the correct diagnosis is critical for genetic risk assessment, and prenatal and preimplantation genetic diagnosis outcomes. We present a case of preimplantation genetic diagnosis (PGD) using array comparative genomic hybridization (aCGH) following trophectoderm biopsy of embryos created after in vitro fertilization for a carrier of an intrachromosomal insertion on chromosome 1 [46,XX, ins(1)(q44q23q32.1)]. The PGD analysis of 6 blastocysts demonstrated 67% unbalanced embryos. No pregnancy was achieved after the transfer of 2 euploid embryos. To the best of our knowledge, this is the first reported case of PGD using aCGH following trophectoderm biopsy for a carrier of an intrachromosomal insertion.

QF-PCR rapid aneuploidy screen and aCGH analysis of cell free fetal (cff) DNA in supernatant of compromised amniotic fluids (AF).

OBJECTIVE: The aim of this study was to determine whether cell free fetal (cff) DNA in residual amniotic fluid (AF) supernatant obtained from bloody, low-volume and late gestation samples can be used for prenatal diagnosis by quantitative fluorescence polymerase chain reaction (QF-PCR) and array comparative genomic hybridization (aCGH). METHOD: A total of 49 compromised AFs were analyzed in this case-control, double-blinded study. The samples were processed through: a conventional cytogenetic approach utilizing Fluorescence in situ Hybridization and/or karyotype (Approach I); QF-PCR analysis to establish the presence of maternal cell contamination (MCC) (Approach II) and a newly proposed approach using AF supernatant cff DNA (Approach III). Data on clinical impact and turn-around-time was collected. RESULTS: Evidence of MCC was not detected in any of the cff DNA samples, and informative results were provided for all cases, including nine aneuploidies. In contrast, the conventional approach (I) failed to provide results either due to MCC or culture failure in a significant proportion of cases. An adequate amount of quality cff DNA was obtained for successful aCGH testing. CONCLUSION: We have shown that it is feasible to isolate pure cff DNA from routinely discarded AF supernatant to perform QF-PCR and microarray analyses, providing timely and informative results even for problematic grossly bloody and otherwise compromised AF samples or culture failures.

Development of a high-resolution Y-chromosome microarray for improved male infertility diagnosis.

OBJECTIVE: To develop a novel clinical test using microarray technology as a high-resolution alternative to current methods for detection of known and novel microdeletions on the Y chromosome. DESIGN: Custom Agilent 8x15K array comparative genomic hybridization (aCGH) with 10,162 probes on an average probe spacing of 2.5 kb across the euchromatic region of the Y chromosome. SETTING: Clinical diagnostic laboratory. PATIENT(S): Men with infertility (n = 104) and controls with proven fertility (n = 148). INTERVENTION(S): Microarray genotyping of DNA. MAIN OUTCOME MEASURE(S): Gene copy number variation determined by log ratio of probe signal intensity against a DNA reference. RESULT(S): Our aCGH experiments found all known AZF microdeletions as well as additional unbalanced structural alterations. In addition to complete AZF microdeletions, we found that AZFc partial deletions represent a risk factor for male infertility. In total, aCGH-based detection achieved a diagnostic yield of ∼11% and also revealed additional potentially etiologic copy number variations requiring further characterization. CONCLUSION(S): The aCGH approach is a reliable high-resolution alternative to multiplex polymerase chain reaction for the discovery of pathogenic chromosome Y microdeletions in male infertility.

Functional characterization of an aminotransferase required for pyoverdine siderophore biosynthesis in Pseudomonas aeruginosa PAO1.

The fluorescent dihydroxyquinoline chromophore of the pyoverdine siderophore in Pseudomonas is a condensation product of D-tyrosine and l-2,4-diaminobutyrate. Both pvdH and asd (encoding aspartate beta-semialdehyde dehydrogenase) knockout mutants of Pseudomonas aeruginosa PAO1 were unable to synthesize pyoverdine under iron-limiting conditions in the absence of l-2,4-diaminobutyrate in the culture media. The pvdH gene was subcloned, and the gene product was hyperexpressed and purified from P. aeruginosa PAO1. PvdH was found to catalyze an aminotransferase reaction, interconverting aspartate beta-semialdehyde and l-2,4-diaminobutyrate. Steady-state kinetic analysis with a novel coupled assay established that the enzyme adopts a ping-pong kinetic mechanism and has the highest specificity for alpha-ketoglutarate. The specificity of the enzyme toward the smaller keto acid pyruvate is 41-fold lower. The enzyme has negligible activity toward other keto acids tested. Homologues of PvdH were present in the genomes of other Pseudomonas spp. These homologues were found in the DNA loci of the corresponding genomes that contain other pyoverdine synthesis genes. This suggests that there is a general mechanism of l-2,4-diaminobutyrate synthesis in Pseudomonas strains that produce the pyoverdine siderophore.