PMC4482096_01
Dysmorphic craniofacial features of the proband with trisomy 9 mosaicism syndrome
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Fig1
Dysmorphic features were visibly evident, including microcephaly, craniofacial asymmetry, long face, ocular hypertelorism, short and upward slanting palpebral fissures, short frenulum of the upper lip, high arched palate, low-set ears and abnormal nasal features including a prominent nasal bridge with a short root, a small fleshy tip and slit-like nostrils (Fig. 1).
Levels of T9 mosaicism in somatic tissues. a. NIPT result for Chr9. The Chr9 plot shows the mean copy number variation per 20 kb sequencing bin (blue line) versus each 20 kb sequencing bin. The upper dashed line indicates the expected position of the blue line for 100 % T9. b. Analysis of white blood cells with fluorescein labeled 9p (green) and rhodamine labeled 9q (red) FISH probes. c. Analysis of white blood cells with 9p and 9q FISH probes. Representative FISH results (B and C) in a single viewing field are shown for two cells as examples of disomy 9 and T9. White arrows indicate the position of FISH signals for Chr9
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Fig2
T9 was 30.1 % (Fig. 2a), suggesting T9 mosaicism. The couple's clinician was informed about the possibility of a T9 mosaic fetus, prompting further prenatal investigation. T9 in 19 of 100 (19 %) cells examined (Fig. 2b). To confirm T9 mosaicism in another tissue type, interphase FISH was also used directly to assess cheek buccal cells. T9 mosaicism was found in 17 of 100 (17 %) cells examined (Fig. 2c). T9 displaying a bi-allelic marker pattern is 2:1, then the observed peak ratios of approximately 10:1 suggest a level of around 20 % T9 mosaicism, which was very similar to levels determined by FISH (Fig. 2b and 2c). Taken together, the proband inheritance pattern for Chr9 STR markers indicated the presence of two distinct cell lines in the child, one with paternal isodisomy 9 in approximately 80 % of somatic cells and T9 in the remaining somatic cells.
QF-PCR analysis of family genomic DNA samples for revealing the nature and origin of T9 mosaicism. Plots show yield of STR PCR products (Y-axis) versus allelic size (X-axis). Blue and black peaks represent 6-FAM and TAMRA labeled allelic products, respectively. The dominant paternal alleles (isodisomy 9) and the minor maternal alleles for informative STR markers D9S925, D9S1118 and D9S1121 that were inherited by the proband are denoted by symbols (*) and (+), respectively. Control marker D13S325 shows two allelic peaks indicating expected disomy 13
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Fig3
T9 mosaicism and parental origin, we applied quantitative fluorescent PCR (QF-PCR) to analyse paternal, maternal and proband allelic patterns of short tandem repeat (STR) Chr9 markers. The alleles of STR markers D9S925, D9S1118 and D9S1121 were found to be informative for determining familial inheritance patterns (Fig. 3).