Department of Morphology and Genetics, Universidade Federal de São Paulo, São Paulo, Brazil.
Am J Med Genet A. 2010 Mar;152A(3):753-8. doi: 10.1002/ajmg.a.33308.
Supernumerary marker chromosomes (sSMC) may or may not be associated with an abnormal phenotype, depending on the presence of euchromatin, on their chromosomal origin and whether they are inherited. Over 80% of sSMCs are derived from acrocentric chromosomes and half of them include the short arm of chromosome 15. Generally, they appear as bisatellited isodicentric marker chromosomes, most of them are symmetric. These chromosomes are normally originated de novo and are associated with mild to severe intellectual disability but not with physical abnormalities. We report on a patient with an SMC studied using classical and molecular cytogenetic procedures (G and C banding, NOR staining, painting and centromeric fluorescent in situ hybridization (FISH), BAC-FISH, and SKY). The MLPA technique and DNA polymorphic markers were used in order to identify its parental origin. The marker chromosome, monosatellited and monocentric, was found to be derived from a maternal chromosome 15 and was defined as 15pter-q21.2. This is the report of the largest de novo monosatellited 15q marker chromosome ever published presenting detailed cytogenetic and clinical data. It was associated with a phenotype including cardiac defect, absence of septum pellucidum, and dysplasia of the corpus callosum.
额外标记染色体（sSMC）可能与异常表型有关，也可能无关，这取决于其是否含有常染色质、染色体来源以及是否遗传。超过 80%的 sSMC 源自近端着丝粒染色体，其中一半包含 15 号染色体的短臂。通常，它们表现为双着丝粒等臂标记染色体，大多数为对称的。这些染色体通常是从头产生的，与轻度至重度智力残疾有关，但与身体异常无关。我们报告了一例使用经典和分子细胞遗传学方法（G 和 C 带、NOR 染色、涂染和着丝粒荧光原位杂交（FISH）、BAC-FISH 和 SKY）研究的 SMC 患者。使用 MLPA 技术和 DNA 多态性标记来确定其亲本来源。标记染色体为单卫星和单中心，来源于一条母源 15 号染色体，定义为 15pter-q21.2。这是迄今为止报道的最大的从头发生的单卫星 15q 标记染色体，提供了详细的细胞遗传学和临床数据。它与一种表型有关，包括心脏缺陷、透明隔缺失和胼胝体发育不良。
