Nucleoli in a pronuclei-stage mouse embryo are represented by major satellite DNA of interconnecting chromosomes.

OBJECTIVE: To investigate the arrangement of chromosomes within pronuclei-stage mouse zygotes. DESIGN: In vitro study. SETTING: Academic medical center. PATIENT(S): None. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Location of major alpha-satellite DNA, centromeres, and telomeres, and relative location of chromosomes. RESULT(S): Chromosomes appeared to be oriented inward by centromeres and to be interconnected by major alpha-satellite DNA, which appeared to be the sole DNA component of the nucleoli. This chromosomal arrangement persisted throughout interphase. Chromosomal painting failed to identify chromosomal ordering within pronuclei. CONCLUSION(S): Pronuclear nucleoli are represented by alpha-satellite sequences of interconnecting chromosomes that hold all chromosomes together during interphase. Chromosomes within the pronucleus are randomly positioned relative to each other.

Spontaneous abortions are reduced after preconception diagnosis of translocations.

PURPOSE: Preimplantation genetic diagnosis of translocations has seldom been attempted. Recently, a genetic test based on analyzing polar bodies at the methaphase stage, following fluorescent in situ hybridization with commercially available whole-chromosome painting DNA probes has been presented. Here we report the use of this method in seven couples in whom the female was a carrier of one of these balanced translocations: 45,XX,der (13q;14q)(q10;q10) (two cases), 46,XX,t(4;14)(p15.3;q24), 45,XX,der(14q;21q) (q10;q10), 46,XX,t(7;20)(q22;q11.2), 46,XX,t(9,11)(p24;q12), 46,XX,t(14;18)(q22;q11), and 46,XX,t(3;8)(q11;q11). METHODS: The original method was improved in two ways. First, centromeric probes for one or both chromosomes involved in the translocation were added to avoid misdiagnosis caused by possible confusion of first polar body monovalent chromosomes (with two chromatids each) with single chromatids. Second, for cases with terminal translocations where commercially available probes do not cover telomere sequences, a telomere probe labeling the translocated fragment was added. RESULTS: A total of 26 abnormal, 18 balanced, and 22 normal eggs was detected. Nine normal and seven balanced embryos were transferred, resulting in eight (50%) implanting, of which one spontaneously aborted. To date, the remainder have produced karyotypically normal or balanced babies and ongoing pregnancies. The rate of spontaneous abortions after preimplantation genetic diagnosis (12.5%) was significantly reduced (P < 0.001) compared to natural cycles in the same patients (95%). CONCLUSIONS: With the above improvements, the test can characterize any translocation of maternal origin and produce a high pregnancy rate and an apparently low frequency of spontaneous abortion.

Molecular mapping of the chromosome 11 breakpoint of t(11;17)(q13;q21) in a t(11;14)(q13;q32)-positive B non-Hodgkin's lymphoma.

The FAU gene is the cellular homologue of the viral FOX sequences in the genome of the Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV); the viral FOX sequences have been shown to increase the transforming capacity of FBR-MuSV in vitro. The human FAU gene has recently been isolated, characterized, and mapped to chromosome band 11q13. Here, we report results of fluorescence in situ hybridization (FISH) analysis which indicate that the FAU gene maps proximally to the putative oncogene BCL1 at 11q13. Furthermore, we identified a t(11;17)(q13;q21) translocation in tumor cells of a t(11;14)(q13;q32)-positive B-cell non-Hodgkin's lymphoma patient by FISH analysis using a FAU containing cosmid clone as molecular probe and by double-colour chromosome painting analysis using chromosome 11- and chromosome 17-specific painting probes. The position of the chromosome 11 breakpoint of the t(11;17) translocation was pinpointed to a human DNA region around the FAU gene of about 40 kbp.