Prenatal diagnosis of mosaic trisomy 8q studied by ultrasound, cytogenetics, and array-CGH

Intrauterine growth retardation associated with precocious puberty and sertoli cell hyperplasia

The original description of patients with Russell-Silver syndrome included precocious puberty, the mechanism of which was unclear. We describe a child with a Russell-Silver syndrome-like phenotype who presented with precocious puberty that was associated with hyperplasia of the Sertoli cells. The patient was found to have an immature cryptorchid testicle; hyperplastic Sertoli cells were also aneuploid carrying trisomy 8. This chromosomal abnormality was present in Sertoli cells only and could not be detected in peripheral lymphocytes, tunica vaginalis, or other, normal, testicular tissue. Sertoli cells in culture showed excess aromatization providing an explanation for the rapid advancement of the patient's bone age. We conclude that in a patient with a Russell-Silver syndrome-like phenotype, Sertoli cell hyperplasia was associated with somatic trisomy 8, increased aromatization, and gonadotropin-independent precocious puberty.

Detection of low-level mosaicism and placental mosaicism by oligonucleotide array comparative genomic hybridization

PURPOSE

To determine the sensitivity of whole-genome oligonucleotide array comparative genomic hybridization for the detection of mosaic cytogenetic abnormalities.

METHODS

Mosaicism sensitivity was evaluated by testing artificially derived whole chromosome and segmental aneuploidies ranging from 0% to 100% abnormal and additional naturally occurring mosaic specimens.

RESULTS

Using combined dye-reversed replicates and an unfiltered analysis, oligonucleotide array comparative genomic hybridization detected as low as 10% and 20-30% mosaicism from whole chromosome and segmental aneuploidies, respectively. To investigate discrepancies between cultured and uncultured specimens, array comparative genomic hybridization was performed on DNA from additional direct product of conception specimens with abnormal karyotypes in culture. Interestingly, 5 of 10 product of conception specimens with double trisomies on cultured cell analysis had only a single trisomy by array comparative genomic hybridization and quantitative polymerase chain reaction on DNA from the uncultured direct specimen, and all harbored the more commonly observed trisomy. Thus, oligonucleotide array comparative genomic hybridization revealed previously unidentified placental mosaicism in half of the products of conception with double-aneuploid conventional karyotypes.

CONCLUSION

Oligonucleotide array comparative genomic hybridization can detect low-level mosaicism for whole chromosome ( approximately 10%) and segmental ( approximately 20-30%) aneuploidies when using specific detection criteria. In addition, careful interpretation is required when performing array comparative genomic hybridization on DNA isolated from direct specimens as the results may differ from the cultured chromosome analysis.

THE APPLICATION OF MICROARRAY BASED COMPARATIVE GENOMIC HYBRIDIZATION IN PRENATAL DIAGNOSIS

Microscopic forms of karyotyping and cytogenetic analysis by means of G-banded chromosome analysis and rapid FISH (fluorescencein situhybridization) on amniotic fluids or chorionic villus samples are at present regarded as the gold standard for prenatal diagnosis of chromosomal anomalies. Nevertheless, up to now the resolution of conventional chromosomal analysis was limited to approximately 4–5 Mb and not smaller than 2 Mb for FISH. Thus numerous common microdeletion syndromes are not detectable by conventional karyotyping. In addition, prenatal cells yield lower band resolution by conventional karyotyping than peripheral white blood cells making detection of subtle abnormalities even more difficult. With the advances in molecular-based techniques, a collaborative effort has led to the standardized method for detection of a restricted set of common chromosomal aneuploidies and microdeletion syndromes such as Down's syndrome, DiGeorge or Angelman syndrome either by rapid FISH and/or quantitative fluorescent PCR (QF-PCR). Even if the presence of particular phenotypic features of microdeletion or duplication syndromes may direct the use of syndrome-specific FISH tests in the postnatal period, syndrome-specific FISH analysis still has a very limited potential and application in the prenatal period due to the limitation in prenatal morphological or imaging diagnosis of many of the syndromes.