Differences in nuclear gene expression between cells containing monomer and dimer mitochondrial genomes

It is known that point mutations and rearrangements (deletions and duplications) of mammalian mitochondrial DNA (mtDNA) can result in mitochondrial dysfunction and human disease. Very little attention has been paid to mtDNA circular dimers (a complex form consisting of two genomes joined head-to-tail) despite their close association with human neoplasia. MtDNA dimers are frequently found in human leukemia, but the clinical relevance of their presence remains unknown. To begin to investigate the role of circular dimer mtDNA in the tumorigenic phenotype, we have created isogenic cell lines containing monomer and dimer mitochondrial genomes and compared the respective nuclear mRNA expression using Affymetrix gene array analysis. Surprisingly, a large number of nuclear gene changes were observed, with one of the largest category of genes being associated with remodeling of the cell surface and extracellular matrix. Since cell growth, migration, apoptosis, and many other cellular processes are influenced by signals initiating from the cell surface, the changes associated with the presence of mtDNA dimers could lead to significant alterations in tumorigenic potential and/or progression.     

Prenatal diagnosis/treatment in families at risk for infants with steroid 21-hydroxylase deficiency (congenital adrenal hyperplasia)

The most common enzymatic defect of steroid synthesis is adrenal steroid 21-hydroxylase deficiency. Inhibited formation of cortisol causes increased pituitary release of ACTH, driving the adrenal cortex to overproduce androgens, whose synthesis does not involve the 21-hydroxylase enzyme. This hormonal setting is established in the embryonic period and affects development of genetic females, misdirecting differentiation of the external genitalia toward male type. At birth, the genitalia are visibly ambiguous (enlarged clitoris, fused labia) or in some cases even male in appearance {phallus with urethral opening, rugated scrotal sac), leading to wrong sex assignment. Adrenal steroid 21-hydroxylase deficiency is the most common basis of female pseudohermaphroditism. These females, however, have normal fertility and potential for gestation (gonads are functional and the internal duct-derived structures are well-formed), thus the sex of rearing should always be female. Management is by life-long hormonal (glucocorticoid) replacement, with surgical correction of the genital ambiguity. Prenatal diagnosis of 21-hydroxylase deficiency, first possible by steroid assay of the amniotic fluid, has utilized HLA typing for identification of loci (antigens B and DR) in close linkage with the 21-hydroxylase gene, and now increasingly relies on DNA analysis for linked HLA or C4 genes or for mutant 21-hydroxylase alleles directly by molecular genetic techniques. The most recent clinical advance is a program of combined prenatal diagnosis with karyotyping and suppression of fetal androgen production in genetic females by steroid administration to the mother. This is the first instance of an inborn metabolic error to be prenatally treated.

A series of 85 managed pregnancies is reported on, including accuracy of diagnosis, response of the mother to steroid treatment, and outcome for treated and untreated male and female fetuses (of 77 born by 6/91). Prenatal diagnosis by current techniques is accurate. Normal growth and development patterns postnatally suggest that dexamethasone treatment is safe.