de Pater J M, Kroes H Y, Verschuren M, van Oppen A C C, Albrechts J C M, Engelen J J M
Department of Biomedical Genetics, University Medical Centre, Utrecht, The Netherlands.
Prenat Diagn. 2005 Feb;25(2):151-5. doi: 10.1002/pd.1097.
Our objective was to characterise a marker chromosome in cultured amniocytes of a fetus with a mos 47,XX,+mar[3]/46,XX[14] karyotype.
The indication for prenatal cytogenetic analysis of cultured amniocytes was advanced maternal age. Classic banding techniques (GTG- and C-banding) were performed. Microdissection combined with reverse painting was used to disclose the exact origin of the marker; the result was confirmed by chromosome painting and FISH with band-specific probes.
Analysis of GTG-banded chromosomes showed a small marker chromosome in 3 of the 17 colonies analysed. Subsequently, C-banding showed no alphoid sequences, suggesting the presence of a neocentromere. The parent's karyotypes were normal. After normal ultrasound findings, the parents decided to continue the pregnancy. Chromosome analysis in peripheral blood after birth demonstrated that the marker chromosome was present in 50% of the lymphocytes. Using microFISH, the marker was further characterised and appeared to be derived from chromosome region (8)(p22 --> pter).
Accurate identification of the marker chromosome was very important for prenatal counselling. Combining the results of GTG- and C-banding analysis with the results of the (micro)FISH, we concluded that the patient's karyotype is: mos 47,XX,+mar.rev ish der(8)(p22 --> pter)[50]/46,XX[50].
我们的目的是对一名核型为mos 47,XX,+mar[3]/46,XX[14]的胎儿培养羊水中的一条标记染色体进行特征描述。
对培养羊水进行产前细胞遗传学分析的指征是产妇年龄较大。采用经典的显带技术（GTG显带和C显带）。微切割结合反向荧光原位杂交用于揭示该标记的确切来源；结果通过染色体涂染和使用带特异性探针的荧光原位杂交进行确认。
对GTG显带染色体的分析显示，在分析的17个克隆中有3个含有一条小的标记染色体。随后，C显带显示无α卫星序列，提示存在新着丝粒。父母的核型正常。在超声检查结果正常后，父母决定继续妊娠。出生后外周血染色体分析表明，标记染色体存在于50%的淋巴细胞中。使用微荧光原位杂交，该标记进一步得到特征描述，似乎源自染色体区域(8)(p22→pter)。
准确识别标记染色体对产前咨询非常重要。将GTG显带和C显带分析结果与（微）荧光原位杂交结果相结合，我们得出患者的核型为：mos 47,XX,+mar.rev ish der(8)(p22→pter)[50]/46,XX[50]。
