Prenatal diagnosis of peroxisomal D-3-hydroxyacyl-CoA dehydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional protein deficiency

Urine-Based Liquid Biopsy for Nonurological Cancers

AIMS

The use of circulating cell-free DNA for detection of cancer genetics has been studied extensively. Liquid biopsy often refers to the use of blood as a minimally invasive source of body fluid for detecting circulating tumor DNA (ctDNA). However, urine collection, which is completely noninvasive, has been shown to also have great promise to serve as an alternate body fluid source for ctDNA. In this review article, we focus on the clinical utility of urine for genetic liquid biopsy of nonurological cancers.

CONCLUSION

Although still in early stages as compared with blood-based liquid biopsy, recent studies have demonstrated the value of urine-based liquid biopsies for: nonurological cancer screening; early detection; monitoring for recurrence and metastasis; and therapeutic efficacy. Overall, the completely noninvasive and patient-friendly nature of the urine-based biopsy warrants further development and offers a promising alternative to blood-based biopsies.

Molecular analysis of genomic DNA allows rapid, and accurate, prenatal diagnosis of peroxisomal D-bifunctional protein deficiency

Prenatal diagnosis was requested for a couple with a previous child affected by the peroxisomal disorder D-bifunctional protein deficiency. Prior analysis of the D-bifunctional protein cDNA sequence from the propositus had shown that it was missing 22 bp. This was subsequently attributed to a point mutation in the intron 5 donor site (IVS5 + 1G>C) of the D-bifunctional protein gene. Consistent with parental consanguinity, the patient was shown to be homozygous for this mutation, which is associated with loss of a Hph 1 restriction site in the genomic sequence. Prenatal testing of the fetus using genomic DNA isolated from uncultured amniocytes indicated that both alleles of the D-bifunctional protein had the IVS5 + 1G>C substitution. The peroxisomal defect was later confirmed biochemically using cultured amniocytes, which were found to have elevated levels of very long chain fatty acids (VLCFA). This is the first report of prenatal diagnosis of D-bifunctional protein deficiency using molecular analysis of genomic DNA.

Molecular basis of D-bifunctional protein deficiency

Peroxisomal disorders appear with a frequency of 1:5000 in newborns. They are caused either by peroxisomal assembly defects or by deficiencies of single peroxisomal enzymes. The phenotypes vary widely: affected humans may die very early in life within a few days to several months as a result of the impairment in essential peroxisomal functions as, for example, in Zellweger syndrome, or they may show only minor disabilities as is in acatalasemia. The deficiency of D-bifunctional protein, an enzyme involved in peroxisomal beta-oxidation of certain fatty acids and the synthesis of bile acids, causes a very severe, Zellweger-like phenotype. A number of different mutations in the gene coding for the enzyme were found in humans causing the total or partial loss of its enzymatic function. This paper gives a review of cases and their molecular basis.

Developmental and pathological expression of peroxisomal enzymes: their relationship of D-bifunctional protein deficiency and Zellweger syndrome

We present the developmental changes of peroxisomal enzymes, catalase, L-bifunctional protein (L-BF) and D-bifunctional protein (D-BF), in the normal brains, and patients with D-BF deficiency, a new peroxisomal disease. D-BF immunoreactivity was observed in controls as early as 13 gestational weeks (GW) and increased with maturation. The adult pattern with fine granule staining of somata and dendrites became apparent in adolescence. L-BF appeared at 20 GW in the cerebral cortex and Purkinje cells and positive glia appeared early in the white matter at 17 GW, and then increased with age. Catalase-positive neurons were identified in the same manner as L-BF, D-BF deficiency in both fetus and infant showed markedly diminished enzyme immunoreactivity. Patients demonstrate reduced D-BF expression. Zellweger syndrome shows decreased expression for the three proteins. This study shows that the peroxisomal enzymes may be closely related to neuronal maturation and gliogenesis in human brain and to disturbance of neuronal migration as seen in Zellweger syndrome significant. D-BF deficiency may exhibit a range of symptoms during the neonatal and early infantile periods some of which may be similar to Zellweger syndrome.