Purpose: Deletions of distal 9p are associated with trigonocephaly, mental retardation, dysmorphic facial features, cardiac anomalies, and abnormal genitalia. Previous studies identified a proposed critical region for the consensus phenotype in band 9p23, between 11.8 Mb and 16 Mb from the 9p telomere. Here we report 10 new patients with 9p deletions; 9 patients have clinical features consistent with 9pϪ syndrome, but possess terminal deletions smaller than most reported cases, whereas one individual lacks the 9pϪ phenotype and shows a 140-kb interstitial telomeric deletion inherited from his mother. Methods: We combined fluorescence in situ hybridization and microarray analyses to delineate the size of each deletion. Results: The deletion sizes vary from 800 kb to 12.4 Mb in our patients with clinically relevant phenotypes. Clinical evaluation and comparison showed little difference in physical features with regard to the deletion sizes. Severe speech and language impairment were observed in all patients with clinically relevant phenotypes. Conclusion: The smallest deleted region common to our patients who demonstrate a phenotype consistent with 9pϪ is Ͻ2 Mb of 9pter, which contains six known genes.These genes may contribute to some of the cardinal features of 9p deletion syndrome. Genet Med 2008:10 (8): 599 -611. Key Words: 9p deletion, FISH, genotype-phenotype correlation, aCGHThe 9p deletion syndrome is characterized by trigonocephaly, moderate to severe mental retardation, low-set, malformed ears, and dysmorphic facial features, such as up-slanting palpebral fissures and a long philtrum. 1,2 Furthermore, abnormal genitalia are found in some 9pϪ patients who have a chromosomal complement of 46, XY, 3 and hypopigmentation has also been described in two independent studies. 4,5 Since the original report of the syndrome in 1973, 6 over 140 cases of 9p deletion have been documented. The breakpoints occur in bands from 9p22 to 9p24, and the large majority of patients have either terminal deletions or translocations involving another chromosome.Previous studies have delineated the size of 9p deletions in an attempt to develop genotype-phenotype correlations. In one large study, Christ et al., 2 characterized the deletion breakpoints in 24 patients with visible 9p deletions and breakpoints at 9p22 or 9p23. Markers D9S274 (14.2 Mb from the telomere) and D9S286 (8 Mb) were absent in all 24 patients with 9pϪ, whereas D9S285 (16 Mb) was present in a subset of these patients. Thus, the minimal deleted segment in this group of patients included 16 Mb of the 9p terminus. Wagstaff and Hemann 4 described a patient with typical features of 9pϪsyndrome and an interstitial deletion between 8 Mb and 19 Mb of 9p. Based on the data of Wagstaff and Hemann, 4 and from their own data, Christ et al., 2 modified their critical region, i.e., the distal 16 Mb of 9p, and concluded that the critical region for the 9pϪsyndrome lies in an ϳ8-Mb region between D9S285 and D9S286, encompassing bands 9p22-9p23.Among a number of recent publicati...

The cause of mental retardation, present in approximately 3% of the population, is unexplained in the majority of cases. Recent reports have suggested that cryptic telomeric rearrangements resulting in segmental aneuploidy and gene-dosage imbalance might represent a significant cause of idiopathic mental retardation (IMR). Two groups of patients with unexplained developmental delay (unselected and selected) and a group of control individuals have been investigated to determine the frequency of submicroscopic telomeric rearrangements associated with IMR and the frequency within the normal population. In contrast to current thinking, our data have shown that true cryptic telomeric rearrangements are not a significant cause of IMR. No fully cryptic abnormalities were detected in our IMR groups, although a semi-cryptic unbalanced telomeric translocation was identified in one selected patient by high-resolution G-band analysis. This abnormality was confirmed and characterised by fluorescence in situ hybridisation (FISH) with telomere-specific probes. A further 13 cytogenetically detected subtle terminal rearrangements were characterised by using multi-telomere FISH. Seven of these had previously been reported as normal, three of which were shown to be interstitial deletions. These cases illustrate the importance of high-resolution analysis to exclude subtle but cytogenetically visible abnormalities prior to subtelomere FISH screening when determining the frequency of cryptic telomeric rearrangements. Unexpectedly, two cryptic telomeric abnormalities were detected among our control individuals, suggesting that submicroscopic telomeric abnormalities may be a not uncommon finding in the general population. Hence, our data have important implications when defining the significance of cryptic telomeric rearrangements detected during screening programmes.

Single gene systems which allow analysis of the molecular nature of induced mutational events in Drosophila are not welldeveloped. The rosy (ry) locus, which encodes the enzyme xanthine dehydrogenase (XDH), is an excellent candidate for the development of such a system [Chovnick et al, 1977a,b]. Newly induced ry mutants can be subjected to a variety of genetic, enzymatic, and immunological tests, and recent cloning of the rosy+ genetic element allows direct examination of new mutants for DNA sequence alterations.In order to determine if mutation induction at the rosy locus would be representative of the genome, we compared mutability at this locus with that of the wellestablished sex-linked recessive lethal test [Vogel and Leigh, 19751. The ka? males carrying the ry+" wild type isoallele [Chovnick et al, 1977bl and Basc males were permitted to feed for 24 hr on 5% buffered sucrose, or on buffered sucrose solutions of MMS, MNU, or EMS at concentrations shown in Table I. The Basc males were then mated with yw females and the SLRL test carried out by standard procedures wurgler et al, 19771. The ka?ry+" males were mated with y females bearing the noncomplementing ry4I allele, and the F1 scored for new ry mutants [Chovnick et al, 1977bl. In analyzing the results shown in Table I, two assumptions were held: a) the SLRL test simultaneously monitors mutation induction at approximately 700 Xchromosomal loci [Abrahamson et al, 19801; and b) the ry locus, which specifies a 150 kd protein monomer, is approximately twice the size of the average Drosophila Abbreviations: EMS, ethyl methanesulfonate; kd, kilodalton; MMS, methyl methanesulfonate; MNU. N-methyl-N-nitrosourea.