Kathelijne Mangelschots

i(12p) in a malignant ovarian tumor

We have found one or more copies of i(12p) in an ovarian germ cell tumor, histologically a yolk sac tumor. This chromosome marker is characteristically associated with germ cell tumors in males. This report indicates that further investigation is necessary to establish the role of the i(12p) marker in the pathogenesis of germ cell tumors also in females.

Cryopreservation as a tool to reduce multiple birth

The potential role of embryo cryopreservation from the point of view of prevention of multiple pregnancies is analysed. Cryopreservation is an unavoidable option in stimulated IVF/intracytoplasmic sperm injection (ICSI), but at the same time an underestimated tool in the prevention of twins. There is a need for an evaluation system not only of the cryotechnology process per se, but also of the true augmenting effect of cryopreservation on the total reproductive potential of a single oocyte harvest. Only cryopregnancies occurring after an unsuccessful fresh cycle (possibly followed by one or more unsuccessful freeze-thaw cycles with embryos from the same harvest) truly reflect the augmentation potential of cryopreservation. This potential is greater than generally thought. First, the efficacy of cryopreservation is suboptimal with survival rates between 30 and 70%. Second, if single-embryo transfer were applied in a much larger proportion of cycles than is presently the case, more embryos would be available for cryopreservation, resulting in more and more successful freeze-thaw cycles. In the future, the combination of elective single-embryo transfer with an optimized cryopreservation programme is likely to become the standard of care for routine IVF/ICSI treatment.

Impact of single embryo transfer on the overall and twin-pregnancy rates of an IVF/ICSI programme

This retrospective cohort study analyses experience with single embryo transfer (SET) in an lVF/intracytoplasmic sperm injection (ICSI) programme over a 3-year period (1998-2000): 1143 IVF/ICSI cycles were initiated, resulting in 1073 embryo transfers (93.9%). In 810 (75.4%) transfers of two (n = 580; 54%) or more than two (n = 230; 21.4%) embryos, 279 ongoing pregnancies (34.4%) were obtained. In total, there were 263 SET (24.5%): 207 of a single top quality embryo, resulting in 102 conceptions (49.3%) with 71 ongoing implantations (34.3%, one monozygotic twin); and 56 of a single non-top quality embryo, resulting in 16 conceptions (28.6%) with 11 ongoing implantations (19 .6% ). The percentage of transfers of a single top quality embryo gradually increased from 10% (1998) to 19% (1999) to 26% (2000). The total multiple pregnancy rate decreased from 34% (1998), to 32% ( 1999) and 22% (2000), without affecting the overall ongoing pregnancy rate per transfer: 38% in 1998; 29% in 1999; and 34% in 2000. The average number of transferred embryos decreased from 2.26 ( 1998) to 1.86 (2000). Transfer of a single, strictly defined top quality day 3 embryo in twin-prone IVF/ICSI patients reduced the multiple/twin-pregnancy rate but not the overall pregnancy rate.

Identification and characterization of normal length nonfluorescent Y chromosomes: cytogenetic analysis, southern hybridization and non-isotopic in situ hybridization.

SummaryIn two female patients with a 45,X/46,X,+mar karyotype the marker chromosomes were identified as normal length nonfluorescent Y chromosomes (nlYnf) using non-isotopic in situ hybridization (NISH) complementary to routine cytogenetic analysis and Southern hybridization. The recognition of the nlYnf as isodicentric in both patients illustrates and confirms the usefulness and importance of NISH in the identification and characterization of this and many other types of complex chromosome rearrangements.

Molecular study of chromosome 15 in 22 patients with Angelman syndrome

DNA studies in 22 families with Angelman syndrome (AS) were performed using the chromosome 15 marker loci D15S9, D15S10, D15S11, D15S12, D15S13, D15S18, D15S24, D15S86, the alpha-actin gene and the GABA β3 receptor gene (GABRB3). Uniparental disomy of chromosome 15 was excluded in all patients. Eighteen AS patients (82%) showed a molecular deletion of chromosome 15q11–q13 with one or more of these markers. No duplications or junction fragments, bridging deletions or duplication breakpoints were observed. The GABRB3 gene was deleted in all deletion-positive patients tested. Analysis of maternal DNA indicated that each deletion was a de novo event. All deletions were of maternal origin; this is in agreement with genomic imprinting in AS.

Analysis of whole-arm translocations in malignant blood cells by nonisotopic in situ hybridization

Whole-arm translocations in five leukemic patients were studied using nonisotopic in situ hybridization with alpha satellite DNA and simple satellite chromosome-specific DNA probes to detect the target sequences. The results show that this technique provides additional information on the involvement of these DNA sequences in whole-arm translocations.

Angelman syndrome in an inbred family

Angelman syndrome (AS) is characterized by severe mental retardation, absent speech, puppet-like movements, inappropriate laughter, epilepsy, and abnormal electroencephalogram. The majority of AS patients (≈ 65%) have a maternal deficiency within chromosomal region 15q11–q13, caused by maternal deletion or paternal uniparental disomy (UPD). Approximately 35% of AS patients exhibit neither detectable deletion nor UPD, but a subset of these patients have abnormal methylation at several loci in the 15q11–q13 interval. We describe here three patients with Angelman syndrome belonging to an extended inbred family. High resolution chromosome analysis combined with DNA analysis using 14 marker loci from the 15q11-q13 region failed to detect a deletion in any of the three patients. Paternal UPD of chromosome 15 was detected in one case, while the other two patients have abnormal methylation atD15S9, D15S63, andSNRPN. Although the three patients are distantly related, the chromosome 15q11-q13 haplotypes are different, suggesting that independent mutations gave rise to AS in this family.

Reciprocal translocation between the proximal regions of the long arms of chromosomes 13 and 15 resulting in unbalanced offspring: characterization by fluorescence in situ hybridization and DNA analysis

SummaryWe describe two female siblings with similar clinical features consisting of hydrocephalus, scaphocephaly, hypotonia, mongoloid eye slant, blepharophimosis, micrognathia, supernumerary mouth frenula and mental retardation. Routine cytogenetic studies in the elder patient did not reveal any abnormality, and initially it was assumed that the syndrome had an autosomal recessive inheritance. However, a slightly larger chromosome 13 was seen in routine G-banded metaphases of the mother and the youngest of the two siblings. A shorter chromosome 15 was detected in the mother only. High resolution banding showed that the abnormal chromosome 13 contained an extra G-positive band at 13q12. The short chromosome 15 in the mother appeared to have a deletion of band q12. Fluorescence in situ hybridization using DNA markers specific to chromosomes 13 and 15 unequivocally showed that the mother was a carrier of a balanced reciprocal translocation t(13;15)(q12;q13), whereas the youngest siblings karyotype was 46,XX,-13,+der(15)t(13;15)(q12;q13)mat, resulting in partial monosomy 13pter→q12 and partial trisomy 15pter→q13. The proband is thus trisomie for the critical region responsible for Prader-Willi syndrome and Angelman syndrome; this was confirmed by DNA analysis demonstrating one paternal and two maternal alleles from multiallelic marker loci mapping to 15q11-q13. This report illustrates the sensitivity and specificity offered by fluorescence in situ hybridization and its usefulness in the diagnosis and delineation of subtle chromosomal rearrangements.

Assignment of the fucosidase pseudogene FUCA1P to chromosome region 2q31----q32

FUCA1P is a pseudogene of the structural fucosidase gene FUCA1. The former has been mapped to human chromosome 2, whereas the latter has been localized to chromosome 1p34----p36. We have further localized FUCA1P to chromosomal band 2q31----q32 by fluorescent in situ hybridization and digital imaging microscopy. This localization was confirmed by linkage analysis between FUCA1P and the COL3A1 gene in 2q24----q32 which gave maximal lod scores of 4.03 at 3% recombination.