Molecular and cytogenetic data for patient 03-46. A. Genotyping for the family of patient 03.46 shows biallelic maternal contribution for alleles proximal to BP3. Informative loci beyond BP3 have only a single maternal allele (D15S1019, D15S1043, D15S184). B. Array CGH shows an overall dosage from BP1-BP3 in the tetrasomic range. The dotted box indicates control probes and positions of the fish clones are indicated. C. Metaphase FISH using probes 142b22 (red) and AC026087 (green) identify the two normal homologues as well as a large der(15) with large confluent signals for the 142b22 and AC026087 probes (inset). D and E. Interphase FISH with the centromeric probe, pcm15 (blue), AC126407 (red) and AC026087 (green) identifies two cell lines, one euploid cell line (D) and one that carries a der(15) chromosome (yellow arrow) in addition to the two normal homologues (white arrows). The der(15) is dicentric and includes four signals for each of the BAC clones. F. Hybridization of interphase nuclei for 03.46 with pcm15 (blue), 142b22 (red) and AC024087 identifies two normal homologues (white arrows), one of which shows an expansion of the NF1/IgH pseudogene region with four signals from the 142b22 probe. The der(15) shows two centromeric signals, and eight signals from the 142b22 probe and four signals from the AC026087 BAC clone. Ordering of the signals suggests a head to tail arrangement for the duplicated segments within the der(15). G. Tissue section from 03-46 (case SS-99-5552) frontal cortex analyses by FISH for CEP15 (green) and GABRB3 (red). Nuclei were counterstained with DAPI (blue). Mosaicism of der(15) was observed in brain nuclei, with 60% of nuclei showing >2 spots per nucleus for CEP 15 or GABRB3 and 40% of nuclei showing ≤2 spots per nucleus for CEP15 and GABRB3. Homologous pairing of 15q11-q13 alleles was observed around the nucleolus in most nuclei, making the counts of FISH signals range from 1–4 spots per nucleus for CEP15 and 1–6 spots per nucleus for GABRB3 out of a total of 149 nuclei counted.