Smith-Lemli-Opitz syndrome in trisomy 13: how does the mix work?

BACKGROUND

Trisomy 13 and Smith-Lemli-Opitz syndrome (SLOS) are both well-recognized multiple congenital anomaly/mental retardation syndromes.

CASE

In this report we describe a male newborn with trisomy 13 who also has features of SLOS, such as 2/3 toe syndactyly and a shawl-like scrotum. Biochemical analysis was consistent with SLOS, and limited molecular analysis revealed 1 mutation in the DHCR7 gene.

CONCLUSIONS

The challenges in establishing the diagnosis of SLOS in this patient are presented and the unique coexistence of the 2 major malformation syndromes is discussed. Given the overlapping phenotype of the 2 syndromes, our report should encourage further research on cholesterol biosynthesis in patients with trisomy 13.

Congenital heart disease reminiscent of partial trisomy 2p syndrome in mice transgenic for the transcription factor Lbh

Partial trisomy 2p syndrome includes a spectrum of congenital heart disease (CHD) that is characterized by complex malformations of the outflow and inflow tracts, defects in cardiac septation, heart position, as well as abnormal ventricular development. Lbh (limb-bud and heart) is a novel, highly conserved putative transcriptional regulatory protein, which displays a unique spatiotemporal gene expression pattern during early mouse heart development. Here we show that human LBH maps to chromosome 2p23, a genomic region related to CHD in partial trisomy 2p syndrome. Remarkably, transgenic overexpression of Lbh in mice throughout the embryonic myocardium from a cardiomyocyte-specific promoter of the cardiac ankyrin repeat protein gene (Carp/Ankrd1) models CHD reported in humans with partial trisomy 2p syndrome. The malformations in Carp-Lbh transgenic mice reflect impaired pulmonary outflow tract valvulogenesis, cardiac septation, inflow tract morphogenesis, as well as abnormalities in ventricular cardiomyocyte growth. Furthermore, we demonstrate that overexpression of Lbh in cultured mammalian cells represses the synergistic activity of key cardiac transcription factors, Nkx2.5 and Tbx5, leading to reduced activation of the common target gene, Anf (Nppa). Strikingly, reduced levels of Anf expression were also observed in embryonic day 9.5 Carp-Lbh transgenic mice. Thus, repression of Nkx2.5 and Tbx5-mediated gene expression by deregulated Lbh may account in part for the cardiac anomalies observed in these mice. Our findings implicate LBH as a candidate gene for CHD associated with partial trisomy 2p syndrome and suggest an important role of Lbh in transcriptional control during normal cardiogenesis.

Nonrandom aneuploidy of chromosomes 1, 5, 6, 7, 8, 9, 11, 12, and 21 induced by the benzene metabolites hydroquinone and benzenetriol

The loss and gain of whole chromosomes (aneuploidy) is common in the development of leukemia and other cancers. In acute myeloid leukemia, the loss (monosomy) of chromosomes 5 and 7 and the gain (trisomy) of chromosome 8 are common clonal chromosomal abnormalities. Here, we have tested the hypothesis that metabolites of the human leukemogen benzene cause a higher rate of gain and loss among the chromosomes involved in leukemogenesis and, as such, are nonrandom and selective in their effects. Human peripheral blood was exposed to two metabolites of benzene, namely, hydroquinone (HQ) and benzenetriol (BT), and the ploidy status of nine different chromosomes (1, 5, 6, 7, 8, 9, 11, 12, and 21) was examined using fluorescence in situ hybridization of metaphase spreads. Poisson regression was used to provide interpretable incidence rate ratios and corresponding P values for all nine chromosomes. Statistically significant differences were found between the sensitivity of the nine chromosomes to gain or loss. Chromosomes 5 and 7 were highly sensitive to loss following HQ and BT exposure, whereas chromosomes 7, 8, and 21 were highly sensitive to gain in comparison to other chromosomes. Significant support for the a priori hypothesis that chromosomes 5 and 7 are more sensitive to loss induced by HQ and BT than the other seven chromosomes was also obtained. These data support the notion that benzene metabolites affect the ploidy status of specific chromosomes more than others and may initiate or promote leukemia induction through these specific effects.

Concurrent generation of subplate and cortical plate neurons in developing trisomy 16 mouse cortex

During embryonic development of the mammalian cerebral cortex, the generation of the marginal zone (MZ) and subplate (SP) precedes that of the cortical plate (CP). MZ and SP neurons are believed to play a 'pioneering' role in directing the organization of the CP and the specificity of connections between the CP and other brain regions. Here we report that this sequential order of neurogenesis is disrupted in the trisomy 16 (Ts16) mouse, a potential animal model of Down syndrome. Bromodeoxyuridine labeling was used to establish the date of generation of postmitotic SP and CP neurons in the somatosensory cortex. As has been previously reported, most SP neurons in euploid (control) cortex were generated on embryonic day 12.5 (E12.5), and production of CP neurons began a day later. In contrast, in the Ts16 cortex, few SP neurons were born on E12.5 and most were generated on E13.5 and E14.5 when CP neurons were also being produced. Thus, in the Ts16 cortex, many CP neurons are born and arrive at their destinations before the normal complement of SP neurons is present. This disruption of the temporal sequence of SP and CP generation may, therefore, interfere with the pioneering functions of the SP during cortical neurogenesis and may alter the connectivity of the cortex. Indeed, using lipophilic membrane tracers to label axonal projections, we found very little thalamocortical innervation of the Ts16 SP at an age when there is extensive innervation of the euploid SP.

Detection of mosaicism for primary trisomies in prenatal samples by QF-PCR and karyotype analysis

OBJECTIVES

QF-PCR can be used to rapidly diagnose primary trisomy in prenatal samples. Our objectives were to estimate the prevalence of primary trisomy mosaicism for chromosomes 13, 18 or 21 in a cohort of prenatal samples, and to compare and contrast the detection of this mosaicism using both QF-PCR and karyotype analysis.

METHODS

Data was collated from all prenatal samples displaying mosaicism for a primary trisomy between June 2000 and March 2004. Levels of mosaicism were estimated and samples were categorised according to the cell population in which the mosaicism was detected.

RESULTS

In a total of 8983 samples, 18 samples (0.20%) displaying mosaicism were detected, including trisomy 13 (three samples), trisomy 18 (seven samples), trisomy 21 (seven samples) and mosaic triploidy (one sample). This included 7 amniotic fluid and 11 chorionic villus samples. Mosaicism was detected by QF-PCR in 12 samples and by karyotype analysis in 8 samples.

CONCLUSIONS

QF-PCR can detect mosaicism when the abnormal cell line contributes at least 15% of the whole sample. Use of both karyotype and QF-PCR analysis leads to the detection of more cases of mosaicism than either test alone.

Prenatal foetal diagnosis of partial trisomy 3q and monosomy 13p due to a maternal balanced rearrangement

The authors describe a case of a male foetus whose ultrasound at 20 weeks' gestation revealed cystic hygroma, cleft lip and ventricular septal defect. Amniotic fluid cytogenetics using GTG banding showed a 46,XY,der(13)t(3;13)(q12;p11.1) rearrangement, and fluorescence in situ hybridization (FISH) delineated the relevant breakpoints. Familial studies identified a maternal balanced translocation involving chromosomes 3 and 13. The post-mortem examination confirmed the prenatal ultrasound findings.

Molecular aspects of Down syndrome

Molecular aspects of Down syndrome (DS), a major genetic cause for mental retardation, commonly associated with trisomy 21 are discussed. Two different hypotheses have been speculated to better understand the disease. One believes that increased gene dosage contributes to the phenotypic abnormalities; the other correlates genetic imbalance with DS pathogenesis. To sustain these hypotheses, different murine models have been developed. Experimental models as well as sequencing of human chromosome 21 helped in speculating a few possible candidate genes for DS. However, the phenotypic changes involved with this neurological disorder vis-a-vis the enhanced number of genes, still remain unexplained. Improvement in screening pattern, model system, as well as better understanding of the disease etiology may help in developing efficacious therapeutic regimes for DS.

High concordance from independent studies by the Children's Cancer Group (CCG) and Pediatric Oncology Group (POG) associating favorable prognosis with combined trisomies 4, 10, and 17 in children with NCI Standard-Risk B-precursor Acute Lymphoblastic Leukemia: a Children's Oncology Group (COG) initiative

Chromosome aberrations have a major role in pediatric acute lymphoblastic leukemia (ALL) risk assignment. The Children's Cancer Group (CCG) and the Pediatric Oncology Group (POG) independently assessed the significance of trisomy for chromosomes 4, 10, and 17 in National Cancer Institute (NCI) Standard- and High-Risk ALL. Data from 1582 (CCG) and 3902 (POG) patients were analyzed. Eight-year event-free survivals (EFS) of 91% (CCG) and 89% (POG) (P < 0.001) were achieved in patients assigned to NCI Standard Risk whose leukemic cells had simultaneous trisomies 4, 10, and 17. Both groups showed the degree of favorable prognostic importance increased with the actual number of favorable trisomies. POG analyses also demonstrated hyperdiploidy (> or =53 chromosomes) was less of an independently significant prognostic factor in the absence of these key trisomies. This finding supported conclusions from previous CCG and POG studies that specific trisomies are more important than chromosome number in predicting outcome in pediatric B-precursor ALL. In NCI Higher Risk patients, the number of favorable trisomies was not prognostically significant, but showed the same trend. Moreover, specific trisomies 4, 10, and 17 remain associated with favorable prognosis in Standard-Risk B-precursor ALL, even in the context of very different treatment approaches between the groups.

Genotype/phenotype analysis in a patient with pure and complete trisomy 12p

Reports on patients with pure and complete trisomy 12p are rare. Up to now, 12 cases have been described in the literature. Here, we report on the genotype/phenotype-correlation of a female patient with a pure trisomy 12p. Conventional cytogenetic studies on peripheral blood chromosomes as well as molecular cytogenetic (fluorescence in situ hybridization, FISH) techniques including whole chromosome painting (WCP), comparative genomic hybridization (CGH), multicolor-banding (MCB) detected a female karyotype with an abberant chromosome 12:46,XX,der(12).ish dup(12)(pter --> q24.3::p11.2 --> pter). In addition to the trisomy 12p specific clinical hallmarks, the patient showed some features of Pallister-Killian syndrome (PKS) such as sparse hair, macroglossia, and epilepsy. These findings contribute to the genotype/phenotype correlation in trisomy 12p patients.

Prenatal diagnosis of trisomy 3 mosaicism

OBJECTIVES

To present the clinical, cytogenetic, and molecular cytogenetic findings of prenatally diagnosed trisomy 3 mosaicism.

CASE AND METHODS

Trisomy 3 mosaicism is rare, and only two cases of prenatally diagnosed trisomy 3 mosaicism have been reported. Amniocentesis, performed for AMA, revealed a karyotype of 47,XX, + 3[8]/46,XX[27]. Periumbilical blood sampling (PUBS) showed 46,XX in 100 cells. Fluorescence in situ hybridization (FISH) analysis using an alpha satellite chromosome 3 probe confirmed the cytogenetic findings. A repeat amniocentesis confirmed mosaicism for trisomy 3 (47,XX, + 3[1]/46,XX[18]). The infant was delivered by elective C-section because of the presence of IUGR and oligohydramnios. The baby had normal physical findings at birth except for symmetric IUGR, apparently resulting from the placental trisomic cell lines. At delivery, chromosome analysis of 50 cells each from blood, placenta, and umbilical cord revealed 46,XX in all cells. FISH analysis of amniotic fluid cells (54 nuclei), peripheral blood (50 nuclei), umbilical cord fibroblasts (57 nuclei), and placental tissue (52 nuclei) demonstrated two signals in 200 nuclei (i.e., 46,XX) and three signals in 13 nuclei (i.e., 47,XX, + 3). At 11 months of age, the baby was progressing normally.

CONCLUSION

A diagnosis of trisomy 3 mosaicism is problematic for patients and clinicians. This is only the third case of trisomy 3 mosaicism identified at amniocentesis. Ultrasound, PUBS, and evaluation of placental tissues and postnatal peripheral blood, were useful in providing information regarding the fetal involvement of trisomy 3. Additional cases of prenatally diagnosed mosaicism for rare trisomies are necessary to more accurately assess the significance of these findings.

Prenatal diagnosis and characterization of an analphoid marker chromosome 16

We report on a fetus with intrauterine growth retardation and multiple malformations diagnosed on ultrasound at 32 weeks. Examination of amniotic fluid cells in culture showed a 47,XY, i(16)(q10), +mar karyotype. Chromosome analysis of both parents was normal. Using spectral karyotyping, we identified the marker chromosome as a mitotically stable acentric marker chromosome derived from chromosome 16. Further studies using subtelomeric fluorescent probes confirmed the presence of an isochromosome for the long arm of chromosome 16 and showed that the acentric marker chromosome derived from the short arm of chromosome 16 leading to a trisomy for the long arm of chromosome 16. After genetic counseling, the parents decided to terminate the pregnancy. Fetal autopsy showed a male fetus with ambiguous external genitalia, cardiac malformation, megacystis and limbs anomalies as observed in other cases of trisomy for the long arm of chromosome 16. In addition, fetal brain examination showed vermian and olfactory bulb hypoplasia.

Cerebellar hypoplasia, zonular cataract, and peripheral neuropathy in trisomy 17 mosaicism

Trisomy 17 mosaicism in liveborns is an extremely rare chromosomal abnormality, with only three cases reported in the literature. Here we describe a 7-year-old boy with trisomy 17 mosaicism. The chromosome abnormality was detected by amniocentesis and was confirmed postnatally in cultured skin fibroblasts. The main clinical features were mental retardation and growth reduction, peripheral motor and sensory neuropathy, hypoplastic cerebellar vermis, zonular cataract, and body asymmetry. In our patient, and in the three earlier described cases, the additional chromosome 17 was detected in skin fibroblasts, not in peripheral lymphocytes. Molecular investigations excluded uniparental disomy of chromosome 17 in our patient. The extra chromosome 17 probably originated from a postzygotic mitotic nondisjunction of the maternal chromosome 17. In most cases of trisomy 17 mosaicism detected in amniocytes the chromosome abnormality seems to be confined to extra-embryonic tissues and clinically normal children are born. If, however, there are also ultrasound abnormalities, the possibility of fetal trisomy 17 mosaicism should certainly be considered. If postnatal karyotyping is limited to blood the diagnosis of trisomy 17 mosaicism could easily be missed. Therefore, we recommend chromosome analysis to be based on cultured skin fibroblasts in all cases where mental retardation is accompanied by postnatal growth retardation, body asymmetry, peripheral neuropathy, and cerebellar hypoplasia or zonular cataract.

Abnormal lymphatic development in trisomy 16 mouse embryos precedes nuchal edema

Ultrasound measurement of increased nuchal translucency is a method of risk assessment for heart malformations and trisomy 21 in human pregnancy. The developmental background of this nuchal edema is still not sufficiently understood. We have studied the process in trisomy 16 mice that show nuchal edema and heart malformations. We used trisomy 16 and wild-type (WT) embryos from embryonic day (E) 12.5 to E18.5. In WT embryos at E13, bilateral jugular lymphatic sacs are visible that share a lymphatic-venous membrane with the jugular vein. We could not in any case discern a valve between these vessels. At E14 in the TS16 embryos, the lymphatic sacs become enlarged showing abnormally thickened endothelium, specifically at the site of the membrane. In these embryos, severe edema develops in the nuchal region. There is a very close colocalisation of the nerves with the vascular structures. The start of reorganization of the jugular lymphatic sac to a lymph node is observed in both wild-type and TS16 but is diminished in the latter. In conclusion, abnormal size and structure of the jugular lymphatic sacs coincides with the development of nuchal edema. A disturbance of lymphangiogenesis might be the basis for increased nuchal translucency that is often observed in diseased human fetuses.

Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma With Trisomy 12 and Focal Cyclin D1 Expression: A Potential Diagnostic Pitfall

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and mantle cell lymphoma usually are distinctly different in regard to clinical presentation, morphology, immunophenotype, and molecular/genetic findings. In spite of this, select cases may show overlapping characteristics and represent a diagnostic challenge. Cyclin D1 immunohistochemical staining is usually envisioned as a definitive method for resolving this differential diagnosis, with positivity supporting a diagnosis of mantle cell lymphoma. We report a case involving a 58-year-old man with a diagnosis of CLL/SLL for several years. A lymph node excision was performed after increased adenopathy was noted in the cervical region. The excised lymph node showed typical morphologic findings of CLL/SLL, including the presence of characteristic proliferation centers. Cyclin D1 staining, using 3 different antibodies, was present in scattered prolymphocytes and paraimmunoblasts, mostly within proliferation centers. Fluorescence in situ hybridization and conventional cytogenetics demonstrated trisomy 12 and an absence of t(11;14) in lymph node tissue. Focal cyclin D1 expression by immunohistochemistry in nodal CLL/SLL is quite unusual and is discussed as a potential diagnostic pitfall.

M-FISH applications in clinical genetics

Until recently, presence of de novo marker or derivative chromosomes was quite problematic for genetic counseling especially in prenatal diagnosis, because characterization of marker and derivative chromosomes by conventional cytogenetic techniques was nearly impossible. However, recently developed molecular cytogenetic technique named Multicolor Fluorescence in Situ Hybridization (M-FISH) which paints all human chromosomes in 24 different colors allows us to characterize marker and derivative chromosomes in a single hybridization. In this study, we applied M-FISH to determine the origin of 3 marker and 3 derivative chromosomes. Marker chromosomes were found to originate from chromosome 15 in two postnatal and one prenatal case. Of these, one of the postnatal cases displayed clinical findings of inv dup (115) syndrome and the other of infertility, and the prenatal case went through amniocentesis due to the triple test results. Karyotypes of the patients with derivative chromosomes were designated as 46,XY,der (21)t(1;21)(q32;p11), 46,XX,der(8)t(8;9)(p23;p22) and 46,XX,der(18)t(18;20)(q32;p11.2) according to cytogenetic and M-FISH studies. All of the M-FISH results were confirmed with locus specific or whole chromosome painting probes. The case with der (8)t(8;9) had trisomy 9(p22-pter) and monosomy 8(p23-pter) due to this derivative chromosome. The case with der(18)t(18;20) had trisomy 20(p11.2-pter) and monosomy 18(q32-qter). Parental origins of the derivative chromosomes were analyzed using microsatellite markers located in the trisomic chromosomal segments. Patients' clinical findings were compared with the literature.

[The results of cytogenetic investigations in 107 couples with recurrent spontaneous abortions from Pomerania-Kujawy region of Poland]

About 10-15% of clinically diagnosed pregnancies end by spontaneous abortion. One of the causes of recurrent abortions is the presence of chromosome aberrations in a parent. The paper presents the results of cytogenetic investigations in 107 couples referred to genetic council clinic because of at least 2 spontaneous abortions. Cytogenetic analysis was performed on peripheral blood lymphocytes after standard 72h PHA-stimulated culture. At least 20 GTG- and CBG-banded metaphases were analyzed in each patient. Fluorescence in situ hybridization technique was used as to precisely define cytogenetic results. Chromosome aberrations were found in 7 couples (6.54%), exclusively in women. Numerical aberration (47,XXX) was present in 1 woman, and balanced structural aberrations in 6 (5.61%). In 3 of them balanced translocations were disclosed: t(7; 19)(p13;p13.3), t(8;16)(q24;q22), and t(3;8)(q21;p21), in 2--inversions: inv(2)(p25q31), inv(17)(p12p13.3), and in 1--der(20). Pericentric inversion of chromosome 9 was found in 3 men. The analysis of nongenetic factors showed that neither age, nor congenital anomalies of uterus could be an important factor causing abortions in analyzed couples with aberrations. However, infections and muta- or teratogenic exposure could contribute to loss of pregnancies in some cases. Authors conclude that karyotype analysis should be an integral part of diagnostics in couples with recurrent abortions.

Partial trisomy 11q syndrome (11q23.1-->11qter) due to de novo t (11q; 13q) detected by multicolor fluorescence in situ hybridisation

In this report we describe the identification of a de novo 46, XX, 13q + by multicolour fluorescence in situ hybridisation (M-FISH), as a partial distal 11q trisomy (11q23.1-->11qter). The clinical phenotype association with this distal 11q trisomy is briefly reviewed.

[Chromosomal aberrations in myelodysplastic syndrome]

AIM

To analyse incidence rate of chromosomal aberrations in myelodysplastic syndromes (MDS), specification of clinicomorphological features of some cytogenetic variants.

MATERIAL AND METHODS

Chromosomal analysis by the method of G-differential staining of chromosomes was made in 209 patients with different variants of MDS. RESULTS; Clonal chromosomal aberrations occured in 60.8%. The following aberrations were found most frequently: deletion of the long arm of the chromosome 5 (del(5q)) - 34.6%, trisomy of chromosome 8 (14.1%), monosomy of chromosome 7 (13.4%), aberrations 3q21q26 (12.6%), aberrations of a long arm of X-chromosome (4.7%), the absence of Y-chromosome (3.1%). Complex aberrations of karyotype were found in 13.5% cases. Chromosomal aberrations determined not only clinical and morphological features but also the prognosis of the disease.

CONCLUSION

Cytogenetic examination is an essential component of MDS patients examination. It allows more precise classification of MDS variant and prognostification of the disease course.

Distal trisomy 10q/partial monosomy 14q: an unusual clinical picture

A case of twin boy with partial trisomy for the distal part of the long arm of chromosome 10 (10q24-->qter) and a concomitant monosomy 14(q32-->qter) is reported. The chromosomal abnormalities resulted from a paternal balanced translocation involving chromosomes 10 and 14. An additional clinical feature was observed, viz. hypoplastic lungs. The proband's phenotype was compared to previously reported patients with partial trisomy 10q or 14q deletion.

Clinical outcome and follow-up of the first reported case of Russell-Silver syndrome with the unique combination of maternal uniparental heterodisomy 7 and mosaic trisomy 7

BACKGROUND

Russell-Silver syndrome (RSS) has been associated with maternal uniparental disomy (UPD) for chromosome 7 although the etiology of the syndrome is still unknown. Cases of RSS associated with maternal UPD7 have involved isodisomies, heterodisomies, and mixed isodisomy with heterodisomy simultaneously. This publication is a follow-up report of the postnatal clinical outcome of the first prenatally suspected case of combined mosaic trisomy 7 with maternal uniparental disomy of chromosome 7 (UPD7).

CASE

The diagnosis of RSS in the proband was suspected prenatally because trisomy 7 mosaicism (47,XX,+7[13]/46,XX[19]) and maternal uniparental heterodisomy 7 were both found in amniotic fluid cells. Cord blood karyotype analysis showed only disomic cells (46,XX[50]), whereas postpartum chorionic villus analysis was completely trisomic for chromosome 7 (47,XX,+7[19]). Postnatally, the diagnosis of RSS was confirmed by physical findings, her trisomy 7 mosaicism was confirmed by cytogenetic analysis of her skin biopsy (47,XX,+7[9]/46,XX[20]) and her UPD7 was confirmed on both peripheral blood and skin biopsy using microsatellite markers. During infancy, the proband experienced growth deficiency, persistent hypoglycemia, and psychomotor developmental delay.

CONCLUSIONS

Trisomic rescue as a life-saving mechanism, with subsequent chromosomal mosaicism in combination with UPD may occur more frequently in RSS than has been reported. Systematic testing of cases suspected prenatally or postnatally would be informative regarding the individual contribution of each factor. Imprinting, loss of heterozygosity for recessive genes, and mosaicism may explain the short stature, asymmetry, and the variable expression of the phenotype. The contribution of these mechanisms to the syndrome should be evaluated in these cases.