Length and somatic mosaicism of CAG and GGN repeats in the androgen receptor gene and the risk of prostate cancer in men with benign prostatic hyperplasia.

BACKGROUND: The most common malignancy in men worldwide is cancer of the prostate and determinants of prostate cancer (PRCa) risk remain largely unidentified. Many candidate genes may be involved in PRCa, such as those that are central to cellular growth and differentiation in the prostate gland. We analysed the polymorphic CAG and GGN repeats sequence in exon 1 of the AR gene to determine if the number of repeats might be an indicator of PRCa risk in patients with BPH. METHODS: The study evaluated 28 patients who presented with PRCa at least 6 years after the diagnosis of BPH and 56 matched patients with BPH who did not progress to PRCa over a comparable period. RESULTS: This study showed no evidence for association between the size of AR CAG and GGN repeats and the risk of the development of PRCa in patients with BPH. However, BPH patients with AR CAG instability had a 12-fold increased risk in development of PRCa. CONCLUSIONS: While independent confirmation is required in further studies, these results provide a potential tool to assist prediction strategies for this important disease.

Ocular manifestations of mosaic trisomy 22: a case report and review of the literature.

Mosaic trisomy 22 is rare, but can be compatible with prolonged life. Patients with mosaic trisomy 22 usually present with intrauterine growth retardation, mental retardation, failure to thrive, and craniofacial asymmetry. We report the case of a five-year-old boy who had a birth weight of 3.8 kg and normal developmental milestones. He presented with unilateral ocular manifestations of ptosis, double elevator palsy, high myopia, and choroidal coloboma involving the macula. Cytogenetic evaluation showed a low level of trisomy 22 in peripheral blood lymphocytes (1 in 100) and in cultured fibroblasts from a conjunctival biopsy of the affected eye (1 in 60). Our case demonstrates the value of chromosomal analysis of the tissues involved rather than just karyotyping of the blood lymphocytes to detect mosaicism in patients with localised and unilateral congenital malformations.

Malignant refractory epilepsy in identical twins mosaic for a supernumerary ring chromosome 19.

We report identical twins with supernumerary ring chromosome 19 mosaicism, who had severe refractory epilepsy at an early age. The epilepsy was dominated largely by severe life-threatening tonic seizures. Both twins died, likely as a consequence of their severe epilepsy. They displayed no dysmorphic features. Eight cases of ring chromosome 19 have been reported in the literature, all to our knowledge without epilepsy. The clinical picture of these twins emphasizes the importance of carrying out a karyotype study on patients with early-onset epilepsy even in the absence of dysmorphic features.

Quantitative determination of mosaic GFP gene expression in tobacco.

A specific form of gene silencing that was observed visually as a mosaic distribution of fluorescent and non-fluorescent cells apparently dispersed at random within tissues was found in a few green fluorescent protein (GFP)-transformed tobacco lines. To characterize this event quantitatively, we studied flow cytometric measurements in GFP-expressing and -silenced cells in T1 and T2 progeny of four selected plants. The proportion of silenced cells varied considerably among the T1 lines but with notable genotype differences. Mosaic expression was inherited into the T2 generation in which the majority of progenies tested exhibited a level of silencing similar to that of their T1 parental plants. However, in some T2 progenies segregation, evident as a decrease or increase in the proportion of fluorescent cells, was observed. We discuss several factors, such as copy number, promoter activity or polyploidy, that may be the possible causes of the gene silencing, but none sufficiently explain the appearance of the mosaic distribution.

PHANTASTICA regulates development of the adaxial mesophyll in Nicotiana leaves.

Initiation and growth of leaf blades is oriented by an adaxial/abaxial axis aligned with the original axis of polarity in the leaf primordium. To investigate mechanisms regulating this process, we cloned the Nicotiana tabacum ortholog of PHANTASTICA (NTPHAN) and generated a series of antisense transgenics in N. sylvestris. We show that NSPHAN is expressed throughout emerging blade primordia in the wild type and becomes localized to the middle mesophyll in the expanding lamina. Antisense NSPHAN leaves show ectopic expression of NTH20, a class I KNOX gene. Juvenile transgenic leaves have normal adaxial/abaxial polarity and generate leaf blades in the normal position, but the adaxial mesophyll shows disorganized patterns of cell division, delayed maturation of palisade, and ectopic reinitiation of blade primordia along the midrib. Reversal of the phenotype with exogenous gibberellic acid suggests that NSPHAN, acting via KNOX repression, maintains determinacy in the expanding lamina and sustains the patterns of cell proliferation critical to palisade development.

Chromosomal abnormalities in fetuses with open neural tube defects: prenatal identification with ultrasound.

OBJECTIVES: To determine the prevalence of chromosomal abnormalities in fetuses with open neural tube defects (NTD) undergoing prenatal chromosome analysis. The role of prenatal ultrasound in detecting those with an underlying chromosomal abnormality was also investigated. METHODS: Over a 6-year period, 144 fetuses with open NTD underwent prenatal chromosome analysis between 12 and 37 weeks of gestation, as part of a prospective, multicenter prenatal diagnosis and counseling program in Chile. This population included 66 fetuses with spina bifida, 46 with acrania/anencephaly, 21 with cephalocele and 11 with iniencephaly. A confident prenatal diagnosis was made in 143 fetuses (99%) and confirmed postnatally in all cases. RESULTS: An underlying chromosomal abnormality was diagnosed in 10 fetuses (7%), six with spina bifida, three with cephalocele and one with craniorachischisis. The prevalence of chromosomal abnormality varied according to the defect present in the fetus, with a 14% (3/21) prevalence among those with cephalocele, 9% (6/66) among those with spina bifida and 2% (1/57) among those with lethal defects such as acrania, anencephaly or iniencephaly. Karyotype results revealed trisomy 18 in seven cases, trisomy 13 in two and mosaicism for a marker chromosome in one. Prenatal ultrasound before the procedure showed that all chromosomally abnormal fetuses had additional findings. The prevalence of chromosomal abnormality in fetuses with spina bifida and cephalocele was higher when chromosome analysis was performed at or before 24 weeks of gestation in comparison to those performed after 24 weeks (5/31 (16%) vs. 4/56 (7%), respectively). However, this difference did not reach statistical significance, probably due to the small number of cases. CONCLUSIONS: A significant number of fetuses with open NTD are chromosomally abnormal. Although prenatal chromosome analysis should be considered in all cases, prenatal ultrasound seems effective in identifying those fetuses with an underlying chromosomal abnormality.

High proportion of mutant osteoblasts is compatible with normal skeletal function in mosaic carriers of osteogenesis imperfecta.

Individuals with mosaicism for the autosomal dominant bone dysplasia osteogenesis imperfecta (OI) are generally identified by having more than one affected child. The mosaic carriers have both normal and mutant cell populations in somatic and germline tissues but are unaffected or minimally affected by the type I collagen mutation that manifests clinically in their heterozygous offspring. We determined the proportion of mutant osteoblasts in skeletal tissue of two mosaic carriers who each have a COL1A1 mutation in a high proportion of dermal fibroblasts. Both carriers had normal height and bone histology; the first carrier had normal lumbar spine measurements (L1-L4), as determined by dual-energy x-ray absorptiometry (Z = +1.17). In cultured cells from the first carrier, studied by labeled PCR and single-cell PCR over successive passages, the collagen mutation was present in 85% of fibroblasts and 50% and 75% of osteoblasts from her right iliac crest and left patella, respectively, with minimal selection. The second carrier was studied by PCR amplification of DNA from autopsy paraffin blocks. The proportion of heterozygous cells was 40% in calvarium, 65% in tracheal ring, and 70% in aorta. Thus, in OI, substantially normal skeletal growth, density, and histology are compatible with a 40%-75% burden of osteoblasts heterozygous for a COL1A1 mutation. These data are encouraging for mesenchymal stem-cell transplantation, since mosaic carriers are a naturally occurring model for cell therapy.

A comprehensive analysis of allelic methylation status of CpG islands on human chromosome 21q.

Approximately half of all human genes have CpG islands (CGIs)around their promoter regions. Although CGIs usually escape methylation, those on Chromosome X in females and those in the vicinity of imprinted genes are exceptions: They have both methylated and unmethylated alleles to display a "composite" pattern in methylation analysis. In addition, aberrant methylation of CGIs is known to often occur in cancer cells. Here we developed a simple HpaII-McrBC PCR method for discrimination of full, null, incomplete, and composite methylation patterns, and applied it to all computationally identified CGIs on human Chromosome 21q. This comprehensive analysis revealed that, although most CGIs (103 out of 149)escape methylation, a sizable fraction (31 out of 149)are fully methylated even in normal peripheral blood cells. Furthermore, we identified seven CGIs showing the composite methylation, and demonstrated that three of them are indeed methylated monoallelically. Further analyses using informative pedigrees revealed that two of the three are subject to maternal allele-specific methylation. Intriguingly, the other CGI is methylated in an allele-specific but parental-origin-independent manner. Thus, the cell seems to have a broader repertoire of methylating CGIs than previously thought, and our approach may contribute to uncover novel modes of allelic methylation.

Triploid/diploid mosaicism (69XXY/46XX) presenting as severe early onset preeclampsia with a live birth: placental and cytogenetic features.

Triploid/diploid mosaicism was diagnosed following karyotyping of an infant with musculo-skeletal abnormalities delivered because of severe preeclampsia. An area of the placenta appeared unusual with histology suggestive of trophoblastic abnormality. The importance of detailed histopathological examination and ploidy and flow cytometry studies where diagnostic uncertainty exists are highlighted.

Tissue and tumor mosaicism of the myotonin protein kinase gene trinucleotide repeat in a patient with multiple basal cell carcinomas associated with myotonic dystrophy.

We describe the third case (to our knowledge) of multiple basal cell carcinoma associated with myotonic dystrophy and carry out a genetic study of the tumor comparing it with healthy skin. We consider that our results show that this association might be not a purely random phenomenon and that the particular genetic characteristics of this disorder might have a role in the pathogenesis of the tumor.

Genetic and clinical mosaicism in a patient with neurofibromatosis type 1.

Patients with typical features of neurofibromatosis type 1 (NF1) limited to a specific body segment are usually referred to as having "segmental NF1", which is generally assumed to be the result of somatic mosaicism for a NF1 mutation. Mosaicism has also been demonstrated at the molecular level in some sporadic cases with phenotypically classic NF1. In the present report, we describe a patient with NF1 disease manifestations throughout the whole body, but leaving a few sharply delineated segments of the skin unaffected, suggestive of revertant mosaicism. A large intragenic deletion was found by mutation analysis using long-range RT-PCR. The intra-exonic breakpoints were characterized in exon 13 and exon 28, resulting in a deletion of 99,571 bp at the genomic level. The presence of two genetically distinct cell populations, confirming mosaicism for this NF1 mutation, was shown by analysis of several tissues. Revertant mosaicism was excluded by demonstrating heterozygosity for markers residing in the deletion region. The findings in this patient demonstrate two things: (1) although the entire body is affected, mosaicism can still be suspected at clinical examination and proven by DNA analysis and skin biopsies; (2) long-range RT-PCR is a feasible method for demonstrating large intragenic deletions in NF1.

Frequent mutation reversion inversely correlates with clinical severity in a genetic liver disease, hereditary tyrosinemia.

Hereditary tyrosinemia type I (HTI), a severe disease affecting primarily the liver, is caused by a deficiency of fumarylacetoacetate hydrolase (FAH). HTI is clinically heterogeneous, with no correlation between genotype and phenotype. Reversion of FAH mutant alleles in livers of HTI patients was reported previously, but the clinical significance of this phenomenon has not been fully documented. In the present study, the mosaic expression of FAH was analyzed by immune cytochemistry in liver specimens from a cohort of 26 French-Canadian HTI patients who underwent liver transplantation and related to the histopathologic status of the liver and the clinical history. Reversion was observed in 88% of patients with reverted surfaces ranging from 0.1% to 85%. Patients with the chronic form had a much higher surface of reversion (average, 36%) than those with the acute form (average, 1.6%) and a lower incidence of liver dysplasia. Within reverted nodules, hepatocytes had a normal appearance and showed no dysplasia. Hepatocellular carcinoma was observed only in FAH-negative regions. In summary, the extent of mutation reversion of the FAH gene in the liver of HTI patients was inversely correlated with the clinical severity of the disease, suggesting that the corrected hepatocytes play a substantial protective role in liver function.

Cystic partially differentiated nephroblastoma, embryonal rhabdomyosarcoma, and multiple congenital anomalies associated with variegated mosaic aneuploidy and premature centromere division: a case report.

A rare association of embryonal genitourinary tumor(s) with cerebral malformations has been reported in eight infants with variegated mosaic aneuploidy (VMA) and premature centromere division. The authors report a new case of cystic partially differentiated nephroblastoma and embryonal rhabdomyosarcoma associated with VMA, premature centromere division, microcephalus, Dandy-Walker malformation, and cataracts. Nonrandom involvement of the chromosomes was found in VMA of the lymphocytes and the skin fibroblasts. In the cultured nephroblastoma cells, hyperdiploidy involving the same group of chromosomes involved in VMA of the somatic cells was observed, suggesting their derivation from the aneuploid population of the somatic cells.

Chromosomal mosaicism on amniotic interphase nuclei detected by multiprobe FISH.

So far classical prenatal detection of chromosome aberrations has been limited to the evaluation of metaphase by means of time-consuming cytogenetic techniques. The MultiVision PGT test enables a simultaneous detection of aneuploidies of chromosomes 13,18, 21, X, and Y, even 24 h after amniocentesis. In the presented case, this test detected prenatally a chromosomal mosaicism 69,XYY[35]/46,XY[65]. This result was not confirmed after birth, by the same test on blood smear. The discrepancy is difficult to explain.

Mosaic mutations of the LIS1 gene cause subcortical band heterotopia.

BACKGROUND: Subcortical band heterotopia (SBH) is a neuronal migration disorder. DCX mutations are responsible for almost all familial cases, 80% of sporadic female cases, and 25% of sporadic male cases of SBH, and are associated with more severe gyral and migration abnormality over the anterior brain regions. Somatic mosaicism has previously been hypothesized in a patient with posteriorly predominant SBH and a mutation of the LIS1 gene, which is usually mutated in patients with severe lissencephaly. The authors identified mosaic mutations of LIS1 in two patients (Patients 1 and 2) with predominantly posterior SBH. METHODS: After ruling out DCX mutations, the authors performed sequencing of the LIS1 gene in lymphocyte DNA. Because sequence peaks in both patients were suggestive of mosaic mutations, they followed up with denaturing high-pressure liquid chromatography analysis on blood and hair root DNA and compared the areas of heteroduplex and homoduplex peaks. A third patient showing the same mutation as Patient 2 but with no evidence of mosaicism was used for comparing the phenotype of mosaic vs full mutation. RESULTS: The two patients with posterior SBH harbored a missense (Arg241Pro) and a nonsense (R8X) mosaic mutation of LIS1. The rate of mosaicism in Patient 1 was 18% in the blood and 21% in the hair roots, whereas in Patient 2 it was 24% and 31% in the same tissues. The patient with a full R8X mutation of LIS1 had severe lissencephaly. CONCLUSIONS: Subcortical band heterotopia can occur with mosaic mutations of the LIS1 gene. Mutation analysis of LIS1, using highly sensitive techniques such as denaturing high-pressure liquid chromatography, should be considered for patients with posteriorly predominant subcortical band heterotopia and pachygyria.

Retinoblastoma associated with chromosomal 13q14 deletion mosaicism.

PURPOSE: To assess the risk of retinoblastoma developing in children with microscopic chromosomal with mosaic deletions involving 13q14. DESIGN: Case report and systematic literature review. PARTICIPANTS: Data on 29 patients with a mosaic and 107 patients with a nonmosaic somatic deletion of chromosome 13q14 were compared. MAIN OUTCOME MEASURES: Age at diagnosis, frequency, and laterality of retinoblastoma. CASE REPORT: A dysmorphic baby, who carried a chromosomal deletion involving 13q14 in 34% of peripheral blood lymphocytes, had neuroradiologic evidence of retinoblastoma at the age of 2 weeks. She developed trilateral retinoblastoma, a pineal neuroblastic tumor, at the age of 10 months. The diagnosis of her tumor was delayed because of misjudgment of risk of retinoblastoma developing. RESULTS: Meta-analysis revealed no difference between children with mosaic and nonmosaic chromosomal deletion of 13q14 regarding the age at diagnosis, laterality of tumor, and presence of family history for retinoblastoma. A lower percentage of somatic cells with mosaic deletion did not predict a higher age at diagnosis or unilateral tumors. No statistically significant difference was noted regarding the presence of mental retardation, dysmorphic features, and anomalies of internal organs between mosaic and nonmosaic deletions. Only 7% (95% confidence interval, 1-23) of 29 patients who had a mosaic chromosomal deletion including 13q14 were not reported to develop retinoblastoma. CONCLUSIONS: Whenever a 13q14 deletion is diagnosed, immediate ophthalmologic evaluation is recommended to ensure prompt diagnosis of retinoblastoma. Mosaic and nonmosaic chromosomal deletions of 13q14 do not differ regarding the risk and type of retinoblastoma developing.

Segmental neurofibromatosis in childhood.

Segmental neurofibromatosis refers to individuals who have manifestations of neurofibromatosis type 1 (NF-1) limited to one area of the body. It results from a post-conceptional mutation in the NF-1 gene leading to somatic mosaicism. Although it is generally considered a rare condition, this report of 39 children with segmental NF-1 demonstrates that it is commonly seen in a pediatric NF-1 referral center. The mean age at diagnosis was 7.8 years (range: 2-25 years). Twenty-nine patients had only pigmentary manifestations of segmental NF-1, including seven who had only café-au-lait macules and 22 who had café-au-lait macules and freckling. Two patients had isolated plexiform neurofibromas; a third patient had a plexiform neurofibroma of the eyelid in addition to ipsilateral dysplasia of the sphenoid wing and Lisch nodules. A 12-year-old girl had an isolated tibial pseudarthrosis. An 8-year-old boy had an isolated optic pathway tumor, which behaved both biologically and radiographically as an NF1-associated tumor. While most children with segmental NF-1 have only localized pigmentary changes, some children will have isolated plexiform neurofibromas, pseudarthroses, or optic pathway tumors. Accurate diagnosis of segmental NF-1 is crucial for both management and genetic counseling.

Molecular characterization of an inherited ring (19) demonstrating ring opening.

Ring chromosomes arise following breakage in both chromosome arms and rejoining of the centric segment at the broken ends or by end-to-end fusion of the telomeres. The phenotype of ring carriers is unpredictable, and developmental abnormalities may occur even when the ring appears to be structurally balanced. This is believed to be due to mitotic instability from abnormal segregation and sister chromatid exchange in somatic cells. Although ring chromosomes usually arise as de novo events, transmittal from mosaic carriers to offspring sometimes occurs. In such cases, offspring with ring mosaicism in combination with a normal cell line remain unexplained. In this report, we used detailed molecular and cytogenetic analyses of a prenatally detected, inherited ring (19) to observe the behavior of the ring chromosome in culture, and to investigate the mechanism of inherited ring chromosome mosaicism.