Three different origins for apparent triploid/diploid mosaics

Four apparent triploid/diploid mosaic cases were studied. Three of the cases were detected at prenatal diagnosis and the other was of an intellectually handicapped, dysmorphic boy. Karyotypes were performed in multiple tissues if possible, and the inheritance of microsatellites was studied with DNA from fetal tissues and parental blood. Non-mosaic triploids have a different origin from these mosaics with simple digyny or diandry documented in many cases. Three different mechanisms of origin for these apparent mosaics were detected: (1) chimaerism with karyotypes from two separate zygotes developing into a single individual, (2) delayed digyny, by incorporation of a pronucleus from a second polar body into one embryonic blastomere, and (3) delayed dispermy, similarly, by incorporation of a second sperm pronucleus into one embryonic blastomere. In three of the four cases, there was segregation within the embryos of triploid and diploid cell lines into different tissues from which DNA could be isolated. In case 2 originating by digyny, the same sperm allele at each locus could be detected in both triploid and diploid tissues, which is supportive evidence for the involvement of a single sperm and for true mosaicism rather than chimaerism. Similarly, in case 4 originating by dispermy, the same single ovum allele at each locus could be detected in diploid and triploid tissues, confirming mosaicism. In the chimaeric case (case 3), the diploid line had the karyotype 47,XY,+16 while the triploid line was 69,XXY. This suggests a chimaera, since, in a true mosaic, the triploid line should also contain the additional chromosome 16. Supporting the interpretation of a chimaeric origin for this case, the DNA data showed that the triploidy was consistent with MII non-disjunction (i.e. involving a diploid ovum). In the mosaic cases (1, 2, 4), there was no evidence of the involvement of a diploid sperm or a diploid ova, and in triploid/diploid mosaicism, an origin from a diploid gamete is excluded, since all such conceptuses would be simple triploids. In one of these triploid/diploid mosaics detected at prenatal diagnosis by CVS, the triploid line seemed to be sequestered into the extra-fetal tissues (confined placental mosaicism). This fetus developed normally and a normal infant was born with no evidence of triploidy in newborn blood or cord blood at three months of age. Copyright © 2003 John Wiley & Sons, Ltd.     

Prenatal diagnosis of trisomy 20 by chorionic villus sampling (CVS): a case report with long-term outcome

A case of prenatally diagnosed non-mosaic trisomy 20 in cells cultured from a chorionic villus sample (CVS)is presented. The term placental karyotype was also non-mosaic trisomy 20. The karyotype of thenewborn was 46,XY/47,XY,+20 in foreskin cultures and in a second skin culture; blood lymphocyte culture was 46,XY. Aside from diffuse, hypopigmentary swirls along the lines of Blaschko observed on hisextremities and trunk, referred to as hypomelanosis of Ito, the patient is clinically normal at 8¾ years ofage. In addition, he is one of the oldest reported cases of mosaic trisomy 20 confirmed after birth forwhich the clinical outcome has been monitored. This case demonstrates that these trisomy 20 findings are compatible with normal psychomotor development and phenotype. Copyright © 2001 John Wiley & Sons, Ltd.     

Pregnancy and postnatal outcome of mosaic isochromosome 20q

Prenatally diagnosed mosaicism for isochromosome 20q is generally reported in association with a normal outcome at birth and is rarely confirmed postnatally. However, the origin of these abnormal cells is unclear and there are few reports of long-term outcomes. We present an additional case of prenatally detected isochromosome 20q, with normal outcome up to age 3.6 years. The abnormal cells, while present at high levels in the amniotic fluid, could not be confirmed in placenta or fetal blood. Nonetheless, based on a review of the literature, the level of isochromosome 20q cells found is associated with risk of abnormal outcome, suggesting a possible effect in some cases. Copyright © 2006 John Wiley & Sons, Ltd.     

Prenatal diagnosis of a mosaic supernumerary marker iso (8p) (tetrasomy 8p): discordance between chorionic villi culture and amniotic fluid karyotypes

We describe the first case of mosaic supernumerary marker iso (8p) displaying a karyotype discordance between chorionic villi (CV) and amniotic fluid (AF) cultures during prenatal cytogenetic diagnosis. In the first trimester, cytogenetic analysis after chorionic villi sampling (CVS) was normal in all metaphases in the short-term cytotrophoblast cell culture, but an undefined supernumerary marker was detected in 60% of mesenchymal cells in the long-term CV culture. Informed of the mosaicism, the couple selected amniotic fluid sampling as a second-trimester confirmatory diagnostic procedure. The supernumerary marker was absent in all of the 25 available AF cells metaphases. The prospective parents received genetic counselling and were informed that the discordance could be interpreted as a placental confined mosaicism or as a true foetal mosaicism with low percentage of affected cells. The couple opted to continue the pregnancy. In the second month of life, the child had abnormal development with severe psychomotor delay and frequent episodes of epilepsy. Postnatal cytogenetic extensive re-evaluation discovered that the previously detected supernumerary marker was indeed an isochromosome (8p) rearrangement present at low frequency in 5% of the blood lymphocytes. Copyright © 2006 John Wiley & Sons, Ltd.     

进一步保持和发扬我党的“真正优势”

本文在全面论述邓小平同志关于“共同的理想”和“铁的纪律”是我党“真正优势”光辉论断的基础上，指出目前我们在保持和发扬“真正优势”方面存在的不足，并认为中国共产党要顺利解决“两大历史性课题”，必须进一步保持和发扬自己的“真正优势”。