A 79-kb paternally inherited 7q32.2 microdeletion involving MEST in a patient with a Silver-Russell syndrome-like phenotype.

Maternal uniparental disomy of human chromosome 7 [upd(7)mat] is well-characterized as a cause of the growth disorder Silver-Russell syndrome (SRS). However, the causative gene is not currently known. There is growing evidence that molecular changes at the imprinted MEST region in 7q32.2 are associated with a phenotype evocative of SRS. This report details a patient with a SRS-like phenotype and a paternally inherited microdeletion of 79 kilobases (35-fold smaller than the previously reported smallest deletion) in the 7q32.2 region. This microdeletion encompasses only five genes, including MEST, which corroborates the hypothesis that MEST plays a central role in the 7q32.2 microdeletion growth disorder, as well as further implicating MEST in upd(7)mat SRS itself.

Porokeratotic eccrine ostial and dermal duct nevus associated with an 11 megabase 3p deletion.

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN) is a rare eccrine hamartoma; the etiology is incompletely understood. A patient presented with congenital, widespread PEODDN. Clinical assessment, histopathologic, cytogenetic, and molecular genetic investigations on affected cells were pursued. Histopathology confirmed PEODDN, and chromosomal microarray on affected tissues identified a mosaic 3p26.3p25.3 deletion in affected tissues. This 11Mb deletion encompasses 47 OMIM genes. We propose that this and other chromosomal deletions may be implicated in some cases of PEODDN, suggesting locus heterogeneity and underscoring the importance of incorporating cytogenetic and molecular investigations into the multidisciplinary care of individuals with suspected mosaic genetic skin disorders.

ALU transposition induces familial hypertrophic cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy (LVH) in the absence of predisposing cardiovascular conditions. Pathogenic variants in at least 16 cardiac sarcomeric genes have been implicated in HCM, most of which act in a dominant-negative fashion. However loss-of-function (haploinsufficiency) is the most common disease mechanism for pathogenic variants in MYBPC3, suggesting that MYBPC3 complete deletion may play a role in HCM pathogenesis. Here, we investigate MYBPC3 complete deletion as a disease mechanism in HCM by analyzing two unrelated patients with confirmed diagnosis of HCM that tested negative by Sanger sequencing analysis. METHODS: MYBPC3 complete deletion was investigated by Multiplex ligation-dependent probe amplification (MLPA) and microarray analyses. The mechanism of deletion was investigated by interrogating the SINEBase database. RESULTS: Patient-1 was diagnosed with nonobstructive HCM in his mid-40s while undergoing assessment for palpitations, and patient-2 with obstructive HCM in his late-20s while undergoing systolic heart murmur assessment for an unrelated illness. MLPA testing revealed a heterozygous deletion of all MYBPC3 exons in both patients. Subsequent microarray testing confirmed these deletions which extended beyond the 5' and 3' ends of MYBPC3. Genomic assessment suggested that these deletions resulted from Alu/Alu-homologous recombination. CONCLUSION: Our results demonstrate that haploinsufficiency resulting from MYBPC3 complete deletion, potentially mediated by Alu recombination, is an important disease mechanism in cardiomyopathy and emphasizes the importance of copy number variation analysis in patients clinically suspected of HCM.

Diagnostic utility of molecular and cytogenetic analysis in lipoblastoma: a study of two cases and review of the literature.

AIMS: Lipoblastoma is a benign neoplasm of embryonic white fat tissue that results from the proliferation of primitive adipocytes, in which histological features can be ambiguous. In order to discriminate between lipoblastoma and other lipogenic and lipomatous tumours, we studied chromosomal alterations and protein expression in two cases of lipoblastoma in infants. METHODS AND RESULTS: Standard cytogenetic analysis, fluorescence in-situ hybridization, array comparative genomic hybridization and Western blotting allowed us to demonstrate the presence of chromosome abnormalities involving the 8q11-13 region containing the pleomorphic adenoma gene 1 (PLAG1), which are classically reported in lipoblastoma, and aberrant expression of PLAG1. CONCLUSIONS: This report illustrates two different tumorigenic pathways implicating PLAG1 in lipoblastoma: amplification through multiple copies of a small marker chromosome derived from chromosome 8, and a paracentric inversion of the long arm of chromosome 8. Both these anomalies induced aberrant expression of PLAG1, emphasizing the role of PLAG1 in tumorigenesis. The aberrant expression of PLAG1 protein has been hypothesized, but this is the first report to demonstrate its occurrence in lipoblastoma.

Correlation of intercentromeric distance, mosaicism, and sexual phenotype: molecular localization of breakpoints in isodicentric Y chromosomes.

Isodicentric chromosomes are among the structural abnormalities of the Y chromosome that are commonly identified in patients. The simultaneous 45,X cell line that is generated in cell division due to instability of the isodicentric Y chromosome [idic(Y)] has long been hypothesized to explain the variable sexual development of these patients, although gonads have been studied in only a subset of cases. We report here on the molecular localization of breakpoints in ten patients with an idic(Y). Breakpoints were mapped by FISH using BACs; gonads and fibroblasts were also analyzed when possible to evaluate the level of mosaicism. First, we demonstrate great tissue variability in the distribution of idic(Y). Second, palindromes and direct repeats were near the breakpoint of several idic(Y), suggesting that these sequences play a role in the formation of idic(Y). Finally, our data suggest that intercentromeric distance has a negative influence on the stability of idic(Y), as a greater proportion of cells with breakage or loss of the idic(Y) were found in idic(Y) with a greater intercentromeric distance. Females had a significantly greater intercentromeric distance on their idic(Y) than did males. In conclusion, our study indicates that the Y chromosome contains sequences that are more prone to formation of isodicentric chromosomes. We also demonstrate that patients with an intercentromeric distance greater than 20 Mb on their idic(Y) are at increased risk of having a female sexual phenotype.

Undifferentiated gonadal tissue, Y chromosome instability, and tumors in XY gonadal dysgenesis.

Patients with XY gonadal dysgenesis are at increased risk of developing gonadal tumors. The etiology of several cases of XY gonadal dysgenesis remains unknown, but X/XY gonadal mosaicism has been hypothesized to play a role. At the histologic level, the presence of persistent primitive sex cords containing immature germ cells in dysgenetic gonads (an entity called undifferentiated gonadal tissue, or UGT) was recently described, and these immature germ cells are thought to be at risk of neoplastic transformation. To further investigate both these aspects, we retrospectively studied the gonads from 30 patients with pure (22) and mixed (8) gonadal dysgenesis. Cytogenetic analyses performed on 35 gonads revealed that structurally abnormal Y chromosomes were lost in a majority of cells from the gonads, explaining the gonadal dysgenesis of patients bearing a rearranged Y chromosome. On the other hand, normal Y chromosomes were less often lost in gonads of patients with gonadal dysgenesis. At the histologic level, 43 of the 51 gonads presented areas characteristic of a streak; 13 of these streak gonads also presented areas of UGT. Structures resembling sex cords but without germ cells were found in many of the streaks not containing UGT, suggesting that UGT was initially present. Of the 13 gonads containing both UGT and a streak, 9 developed a tumor. The proximity of UGT with the tumors as well as the immunostaining patterns (PLAP+, OCT3/4+, and CD117/KIT+) suggests that germ cells found in UGT are a risk factor for gonadal tumors.

Coexistence of a choriocarcinoma and a gonadoblastoma in the gonad of a 46,XY female: a single nucleotide polymorphism array analysis.

Females with 46,XY complete gonadal dysgenesis are at significant risk of developing germ cell tumors, mostly gonadoblastomas. We present here the case of 2 half-sisters, sharing the same father, diagnosed with 46,XY complete gonadal dysgenesis. The 1st sister developed a gonadoblastoma and an invasive dysgerminoma, whereas the 2nd sister developed a gonadoblastoma and an invasive choriocarcinoma within the same gonad. No SRY mutation, chromosome abnormalities, or mosaicism were detected in blood. Single nucleotide polymorphism (SNP) profiling of the choriocarcinoma revealed a complex hyperdiploid pattern with gains of 1 to 4 copies of material from several autosomes, as well as the loss of the Y chromosome and a homozygous SNP profile without copy number change for the X chromosome. Our results are in agreement with the recurrent chromosome gains and losses previously published in germ cell tumors, and the coexistence of both tumors within the same gonad suggests that choriocarcinomas may derive from gonadoblastomas.

Male pseudohermaphroditism and gonadal mosaicism in a 47,XY,+22 fetus.

Trisomy 22 syndrome manifestations include cranial and facial anomalies. Ambiguous genitalia have been described in some fetus, but histological examination of the gonads has been rarely provided. We report here the first case of a male pseudohermaphrodite fetus with non-mosaic full trisomy 22 in amniocytes and presenting with ambiguous external genitalia, testes, and a uterus. In this case, we have further analyzed cytogenetically gonadal and uterine tissues. FISH analyses on paraffin-embedded gonads and uterus indicated the presence of two cell lines: XY and monosomy X, with 22%-50% of uterine cells having monosomy X, while 85%-100% of right and 77%-96% of left testicular cells were XY. The distribution of sex chromosomes observed in these tissues could explain the sexual differentiation observed in this fetus. On the other hand, this phenotype could also have resulted from cryptic anomalies in one or several genes implicated in sexual differentiation. Further evidence is thus needed before identifying the true cause of pseudohermaphroditism in our patient.