Abstract A physical disruption of the Prader‐Willi syndrome (PWS) chromosome region is thought to cause PWS. We describe 2 girls with PWS phenotype, who had unique chromosome 15 abnormalities. The first patient showed mosaicism: 45,XX,t(15;15)(qter→p11.1::q11.200→ qter)/46,XX,t(15;15)(qter → p11.1::q11.200→ qter), + mar. The band 15q11.2 apparently remained intact in the t(15;15) chromosome, and the mar chromosome was considered as r(15) (p11.1q11.1). The second patient had a karyo‐type of 47,XX,del(15)(q11.200→q11.207), + idic (15)(pter → q11.1::q11.1→pter). The complex breakage and reunion involving the 15q11.2 regions of the father's homologous chromosomes 15 at meiosis appeared to have resulted in the idic(15) and the del(15) chromosomes. These cytogenetic findings suggest that the PWS chromosome region may be localized on the very proximal portion of band 15q11.2.
Inwardly rectifying K<sup>+</sup> (Kir) channels play important roles in various cellular functions in excitable and non-excitable cells. We recently cloned the human genes encoding the Kir channel subunits Kir2.2v (KCNJNl) and Kir2.2 (KCNJ12). However, the physiological role of Kir2.2v has not yet been clarified. Fluorescence in situ hybridization analysis of human metaphase chromosomes assigned both genes to 17p11.2→p11.1. The presence of hybridization signals in the paracentromeric regions of both chromosomes 17 from two Smith-Magenis syndrome (SMS) patients indicated that Kir2.2v and Kir2.2 are not located within the minimum critical region of this syndrome.
Abstract Two patients with monosomy for the distal portion of the short arm of chromosome 3 are described. Chromosome analysis on prometaphase cells demonstrated a karyotype of 46,XX, del(3) (p25.3) in one patient and 46,XX, r(3)(p26.1q29) in the other. The former patient showed characteristic clinical manifestations of the 3p‐ syndrome, including growth failure, mental retardation, microcephaly with a flat occiput, triangular face, synophrys, blepharoptosis, hypertelorism, broad and flat nose, long philtrum, downturned mouth, micrognathia, apparently lowset and malformed ears, finger abnormalities, and deafness. The latter patient had a nonspecific phenotype with mental retardation, growth failure and microcephaly. Karyotypephenotype comparisons in the present cases and 16 previously reported cases with deficiency of the distal portion of 3p suggests that deficiency of the 3p25.3 band is critical to produce the main clinical manifestations of the del(3p) syndrome.
