Tetrasomy 12p--unusual presentation in CVS

Leveraging chorionic villus biopsies for the derivation of patient-specific trophoblast stem cells

Human trophoblast stem (TS) cells are an informative in vitro model for the generation and testing of biologically meaningful hypotheses. The goal of this project was to derive patient-specific TS cell lines from clinically available chorionic villus sampling biopsies. Cell outgrowths were captured from human chorionic villus tissue specimens cultured in modified human TS cell medium. Cell colonies emerged early during the culture and cell lines were established and passaged for several generations. Karyotypes of the newly established chorionic villus-derived trophoblast stem (TS CV ) cell lines were determined and compared to initial genetic diagnoses from freshly isolated chorionic villi. Phenotypes of TSCV cells in the stem state and following differentiation were compared to cytotrophoblast-derived TS (TS CT ) cells. TSCV and TSCT cells uniformly exhibited similarities in the stem state and following differentiation into syncytiotrophoblast and extravillous trophoblast cells. Chorionic villus tissue specimens provide a valuable source for TS cell derivation. They expand the genetic diversity of available TS cells and are associated with defined clinical outcomes. TSCV cell lines provide a new set of experimental tools for investigating trophoblast cell lineage development.

Structural brain abnormalities in Pallister-Killian syndrome: a neuroimaging study of 31 children

BACKGROUND

Pallister-Killian syndrome (PKS) is a rare genetic disorder caused by mosaic tetrasomy of 12p with wide neurological involvement. Intellectual disability, developmental delay, behavioral problems, epilepsy, sleep disturbances, and brain malformations have been described in most individuals, with a broad phenotypic spectrum. This observational study, conducted through brain MRI scan analysis on a cohort of patients with genetically confirmed PKS, aims to systematically investigate the neuroradiological features of this syndrome and identify the possible existence of a typical pattern. Moreover, a literature review differentiating the different types of neuroimaging data was conducted for comparison with our population.

RESULTS

Thirty-one individuals were enrolled (17 females/14 males; age range 0.1-17.5 years old at first MRI). An experienced pediatric neuroradiologist reviewed brain MRIs, blindly to clinical data. Brain abnormalities were observed in all but one individual (compared to the 34% frequency found in the literature review). Corpus callosum abnormalities were found in 20/30 (67%) patients: 6 had callosal hypoplasia; 8 had global hypoplasia with hypoplastic splenium; 4 had only hypoplastic splenium; and 2 had a thin corpus callosum. Cerebral hypoplasia/atrophy was found in 23/31 (74%) and ventriculomegaly in 20/31 (65%). Other frequent features were the enlargement of the cisterna magna in 15/30 (50%) and polymicrogyria in 14/29 (48%). Conversely, the frequency of the latter was found to be 4% from the literature review. Notably, in our population, polymicrogyria was in the perisylvian area in all 14 cases, and it was bilateral in 10/14.

CONCLUSIONS

Brain abnormalities are very common in PKS and occur much more frequently than previously reported. Bilateral perisylvian polymicrogyria was a main aspect of our population. Our findings provide an additional tool for early diagnosis.Further studies to investigate the possible correlations with both genotype and phenotype may help to define the etiopathogenesis of the neurologic phenotype of this syndrome.

Mosaic Trisomy 12 Associated with Overgrowth Detected in Fibroblast Cell Lines

Mosaic trisomy 12 is a rare anomaly, and only 9 cases of live births with this condition have been reported in the literature. The clinical phenotype is variable, including neuropsychomotor developmental delay, congenital heart disease, microcephaly, cutaneous spots, facial asymmetry, prominent ears, hypotonia, retinopathy, and sensorineural hearing loss. A 2-year-old female presented with neuropsychomotor developmental delay, prominent forehead, dolichocephaly, patchy skin pigmentation, and unexpected overgrowth at birth. Cytogenetic analysis of her peripheral blood showed normal results, suggesting the presence of a chromosomal alteration in other tissues. Further studies using G-banding and FISH performed on fibroblasts from both hyper- and hypopigmented regions identified a 47,XX,+12/46,XX karyotype. To the best of our knowledge, no patients with mosaic trisomy 12 associated with overgrowth have been reported to date. Congenital overgrowth and neonatal overgrowth have been frequently linked to Pallister-Killian syndrome (PKS; OMIM 601803). This case suggests the possibility of an association of genes present in the 12p region with fetal overgrowth, considering that chromosomal duplications could lead to an increase in the production of aberrant transcripts and disturbing gene dosage effects. This case highlights the importance of cytogenetic analysis in different tissues to provide relevant information to the specific genotype/phenotype correlation.

Targeted prenatal diagnosis of Pallister-Killian syndrome

OBJECTIVE

To present five new cases of prenatally diagnosed Pallister-Killian syndrome (PKS) and to propose an approach for a targeted diagnosis.

METHOD

We retrospectively analyzed ultrasound findings and cytogenetic results in PKS. We also searched through dysmorphology databases for features occurring in PKS that could potentially be seen in prenatal ultrasound examination.

RESULTS

On the basis of collected data, frequent and distinctive features in fetuses with PKS were established. The most appropriate material and method of testing were proposed. Rhizomelic limb shortening, diaphragmatic hernia, thickened nuchal fold, increased prenasal thickness, polydactyly and polyhydramnios were frequent and distinctive findings in fetuses with PKS. Amniocentesis was the most frequent prenatal procedure for material collection. Percentage of aneuploid cells was higher in amniotic fluid than in cord blood. Cytomolecular tests were useful as confirmation as well as preliminary tests. Cytogenetic identification of the isochromosome was done in all cases except one.

CONCLUSIONS

In case of ultrasound evaluation of features frequent and distinctive for PKS in second and third trimesters of pregnancy, targeted diagnosis should be considered. Amniotic fluid instead of cord blood collection is preferable. Communication with the laboratory is important because modification of routine procedures enhances a chance for correct diagnosis. © 2017 John Wiley & Sons, Ltd.

Pallister-Killian Syndrome: Rapid Decrease of Isochromosome 12p Frequency during Amniocyte Subculturing. Conclusion for Strategy of Prenatal Cytogenetic Diagnostics

Pallister-Killian syndrome (PKS) is characterized cytogenetically by mosaic tetrasomy of chromosome 12p. Routine prenatal diagnosis of PKS is still complicated because of the difficulties of discriminating between the supernumerary isochromosome 12p and the duplication 21q and because of the variable level of mosaicism. The frequency of cells with an extra metacentric chromosome i(12)(p10) is usually determined by tissue-limited or tissue-specific mosaicism. We demonstrated a decrease of the abnormal clone with extra i(12p) in the amniotic fluid cells of the PKS fetus during amniocyte subculturing. The rapid loss of the i(12p) in the course of amniocyte subculturing should be the focus of attention during prenatal karyotyping. This is especially necessary for cultures with slow growth, which require further interpretation of the result during cytogenetic diagnosis of PKS.

Tetrasomy 12p (Pallister-Killian syndrome): difficulties in prenatal diagnosis

PURPOSE

We report a rare case of Pallister-Killian syndrome diagnosed prenatally with increased nuchal translucency during screening for trisomy 21.

MATERIALS AND METHODS

Echografic and postmortem examination of the fetus, G-banded chromosome and FISH analysis on short- and long-term chorion villous sampling (CVS) culture.

RESULTS AND DISCUSSION

Cytogenetic analysis revealed a supernumerary isochromosome 12p after long-term culture whereas a normal cell line was detected in short-term culture only. Sonografic examination in 17-weeks' gestation showed further increase of the NT and the additional presence of brachymelia, diaphragmatic hernia and a marked dextroposition of the heart. Termination of the pregnancy was performed. The cases of PKS karyotypically confirmed on CVS are reviewed, and cytogenetic and sonographic aspects of the prenatal diagnosis of PKS are discussed.

Pallister-Killian syndrome: Multiband FISH of tetrasomy 12p

Two patients with mosaicism for tetrasomy 12p are described. One was diagnosed at the age of 14 years with severe mental retardation and other dysmorphologic findings and abnormal skin pigmentation. Chromosome analysis of a blood sample showed a normal female karyotype. A skin biopsy specimen showed mosaicism for a marker chromosome. The other patient was diagnosed prenatally, from a chorionic villus sample, but only in the direct preparation. Mosaicism for a marker chromosome was demonstrated. The ultrasound examination revealed no abnormalities. Multicolor and multiband fluorescence in situ hybridization analyses showed that the marker chromosome was derived from chromosome 12p, which confirmed the diagnosis of Pallister-Killian syndrome in both patients. To our knowledge, this is the first report of the use of these fluorescence in situ hybridization techniques in Pallister-Killian syndrome whereby the nature of the marker chromosome could be confirmed to be derived from chromosome 12p.