Partial deletion of the short arm of chromosome 3

Distal 3p deletion syndrome: detailed molecular cytogenetic and clinical characterization of three small distal deletions and review

The distal 3p deletion syndrome is characterized by developmental delay, low birth weight and growth retardation, micro- and brachycephaly, ptosis, long philtrum, micrognathia, and low set ears. We have used FISH and BACs in order to map three 3p deletions in detail at the molecular level. The deletions were 10.2-11 Mb in size and encompassed 47-51 known genes, including the VHL gene. One of the deletions was interstitial, with an intact 3p telomere. In nine previously published patients with 3p deletions, the size of the deletion was estimated using molecular or molecular cytogenetic techniques. The genotype, including genes of interest, and the phenotype of these cases are compared and discussed. The localization of the proximal breakpoint in one of our patients suggests that the previously identified critical region for heart defects may be narrowed down, now containing three candidate genes. We can also conclude that deletion of the gene ATP2B2 alone is not enough to cause hearing impairment, which is frequently found in patients with 3p deletion. This is the third reported case with an interstitial deletion of distal 3p.

A terminal deletion of the short arm of chromosome 3: karyotype 46, XY, del (3) (p25-pter); a case report and literature review

We describe a boy with a deletion of the short arm of chromosome 3; (46, XY, del (3) (p25-pter) who presented several minor craniofacial anomalies at birth. Only 34 cases of small distal 3p deletion have been described in the literature, seven of them showed hearing loss and four of the 34 cases had brain anomalies. But in none of the 34 cases the middle and internal ear were radiographically examined. Despite the severe hearing loss detected by auditory brainstem evoked responses (ABR), computerized tomographic scanning (CT-scan) of the ear showed a normal anatomy in this patient. The head CT-scan and magnetic resonance imaging (MRI) disclosed a hypoplastic corpus callosum and an enlargement of the lateral ventricles.

Autosomal imbalance syndromes: genetic interactions and the origin of congenital malformations in aneuploidy syndromes

In some autosomal imbalance syndromes an additional imbalance interferes with the occurrence of the anomalies typical of the syndrome itself. For example, polydactyly was found in patients with "pure" del(3p) more frequently (11/23) than in patients where these deletions were associated with different partial trisomies (2/28). The opposite situation was shown in del(7q) syndrome where various defects of the holoprosencephalic group were found to be rarer in patients with "pure" deletions, than in cases with simultaneous occurrence of various partial trisomies. It suggests the importance of gene interaction in determining the phenotypic picture of autosomal imbalance syndromes.

Physical mapping of chromosome 3p25-p26 by fluorescence in situ hybridisation (FISH)

As part of our effort to isolate and characterise the von Hippel-Lindau (VHL) disease gene, we constructed a physical map of chromosome 3p25-26 by fluorescence in situ hybridisation (FISH) studies on a panel of cytogenetic rearrangements involving this region. Biotinylated cosmid and lambda probes were hybridised to metaphase chromosome spreads and positioned with respect to each cytogenetic breakpoint. These studies unequivocally established the order of five loci linked to the VHL disease gene: cen-(RAF1,312)-D3S732-D3S1250-D3S601-D3S18 -pter and determined the position of three other probes within this map. These results ordered RAF1 and D3S732 for the first time, confirmed the localisation of D3S1250 between RAF1 and D3S601 and determined the position of D3S651 with respect to other chromosome 3p25-p26 loci. The establishment of an ordered set of cytogenetic aberrations will enable the rapid assignment of polymorphic and nonpolymorphic cloned sequences within the chromosome region 3p25-p26.

Terminal deletion of the short arm of chromosome 3

A boy with growth and mental retardation, flat occiput, high and broad forehead, blepharoptosis, narrow palpebral fissures, low set, malformed ears, short neck, anal atresia, deep sacral dimple is reported. High-resolution banding analysis showed terminal deletion of the short arm of chromosome 3 (46,XY,del(3)(p25.3)). Deletions of the short arm of chromosome 3 are relatively rare. The clinical features of the patient are compared with those of 19 previously reported cases.

De novo ring chromosome 3: a new case with a mild phenotype

We report an 18 year old female with a de novo ring chromosome 3 found after investigation for short stature. Her karyotype was interpreted as 46,XX, r(3)(p26.2q29). Her phenotype is milder than previously reported cases and illustrates the mild end of the spectrum of the ring chromosome 3 phenotype.

Mother and son with deletion of 3p25-pter

We report on a mother and son with a 3p25-pter deletion. Both have postnatal growth retardation, mental retardation, apparently low-set or malformed ears, and telecanthus. The mother also has ptosis and multiple joint pains, while the son has a long philtrum and anteverted nares. These phenotypes are compared to those of other 3p- patients. Both patients have many manifestations previously described. The son appears to be more severely affected than the mother.

Insertional translocations: report of two new families and review of the literature

We describe two families with insertional translocations. In the first, a large family ascertained because of repeated pregnancy loss, the insertional translocation, ins(1;3)(q32;p13pter), was found to be segregating through three generations. In the second family, ascertained through a proposita with congenital malformations, multiple spontaneous abortions also occurred. The father had an insertional translocation, inv 4(p14,q21.1)ins(7,4)(q32;q21.1 q23). These cases illustrate that recurrent fetal wastage may be caused by insertional translocations and in fact may be the only clinical manifestation of this unusual type of chromosome rearrangement.