The tricho-rhino-phalangeal syndrome(s): chromosome 8 long arm deletion: is there a shortest region of overlap between reported cases? TRP I and TRP II syndromes: are they separate entities?

Human chromosome 8

The role of human chromosome 8 in genetic disease together with the current status of the genetic linkage map for this chromosome is reviewed. Both hereditary genetic disease attributed to mutant alleles at gene loci on chromosome 8 and neoplastic disease owing to somatic mutation, particularly chromosomal translocations, are discussed.

Higher resolution banding techniques in the clinical routine

Experience with higher resolution banding techniques is described. Cell synchronization and different chemicals which delay the mitotic condensation process were tried. None of these agents alone was able to induce undercondensation in a sufficient way in any of the patients investigated. Of the banding techniques, GTG banding proved preferable, but in some special cases RBA banding will be more informative.

Langer-Giedion syndrome with del 8 (q24.13-q24.22)

An 8-year-old boy with the features of Langer-Giedion syndrome except for short stature is described. Chromosome analysis using high resolution G-banding techniques revealed an interstitial deletion of the long arm of chromosome 8:46,XY,del(8)(q24.13-q24.22).

Tricho-rhino-phalangeal syndrome type I in a Belgian family

We report three cases of tricho-rhino-phalangeal syndrome (TRPS) type I in a Belgian family. They presented typical characteristics such as a pear-shaped nose, and short, deformed fingers with cone-shaped epiphyses of some middle phalanges of the hands. Hair growth was practically normal in our patients, except for some narrowing of the lateral part of the eyebrows. Perthes-like hip dysplasia was documented in two of our cases. The proband presented at the age of 31 with Kienböch's disease of the right wrist. Blood and urine analysis showed no clear anomalies. In this patient, echography revealed a renal cyst containing a stone. The relationship of these findings to TRPS is discussed.

Cytogenetics of Mendelian mutations associated with cancer proneness

About 5% of Mendelian mutations displaying neoplastic tendencies are associated with chromosomal aberrations. The best established examples are retinoblastoma and del(13)(q14) and aniridia-Wilms' tumor and del(11)(p13). Evidence suggests that both mutations behave as dominant traits in the individual and as recessive traits in the cells. DNA analysis indicates that tumorigenesis arises from homozygosisty for the mutant allele at these loci, as a consequence of mitotic nondisjunction or from a mitotic recombination event. An additional argument for this conclusion is provided by the demonstration of duplication of 11p15 in some patients with the Beckwith-Wiedemann syndrome, which is complicated often by Wilms' tumor and other embryonal tumors. Data obtained with molecular probes have shown that also rhabdomyosarcoma and hepatoblastoma arise by homozygosity for a mutant allele at a locus on 11p, suggesting ontogenic relatedness of these tumor types. Additional examples of Mendelian mutations associated with chromosome deletions and neoplasia include Langer-Giedion syndrome with multiple exostoses and del(8)(q24.1), multiple endocrine neoplasia and del(20)(p12.2). While the presence of specific chromosome changes in subjects with high susceptibility to neoplasia does pinpoint the location of DNA sequences involved in the predisposition to certain types of cancers, selected Mendelian mutations associated with chromosome instability and cancer proneness may elucidate biological principles of cell proliferation and transformation. However, our current knowledge of mechanisms resulting in increased frequency of chromosome breakage and cancer susceptibility in ataxia-teleangiectasia, Fanconi's anemia, Bloom's syndrome, and similar conditions are still very incomplete.

A final word on the tricho-rhino-phalangeal syndromes

Chromosomal findings in the majority of cases of TRP II (or Langer-Giedion) syndrome and in some cases of TRP I syndrome lead to the conclusion that the former is due to a deletion extending from 8q24.11 to 8q24.13 whereas the latter is caused by an even smaller deleted segment, namely 8q24.12. A case of tricho-rhino-phalangeal syndrome type I with a mosaic deletion of band 8q24.12 is described.

Integrity of the thyroglobulin locus in tricho-rhino-phalangeal syndrome II

The thyroglobulin gene has been mapped to chromosome band 8q24 by several investigators. This is the band implicated in the causation of Langer-Giedion syndrome (tricho-rhino-phalangeal syndrome II). We have examined a restriction fragment length polymorphism at the thyroglobulin locus in a patient with Langer-Giedion syndrome and 8q deletion in order to: (1) localize the Langer-Giedion deletion more precisely, (2) define the relative map positions of the thyroglobulin gene and the Langer-Giedion locus. The results indicate that the locus of the thyroglobulin gene is intact in the patient with an interstitial deletion of proximal band 8q24.1 which confirms its more distal localization reported earlier by Bergé-Lefranc et al. (1985). It also assigns the critical region for the causation of Langer-Giedion syndrome to the proximal part of band 8q24, viz. 8q24.11----q24.13.

Tricho-rhino-phalangeal syndrome without exostoses, wih an interstitial deletion of 8q23

We report on a patient with the Tricho-Rhino-Phalangeal syndrome (TRPS) with normal mentation, without exostoses and with a partial microdeletion of 8q23. Although she had the phenotypic characteristics of TRPS Type I, karyotypic analysis demonstrated the 8q-microdeletion usually associated with TRPS Type II, in which exostoses are present. Our patient represents the second reported instance of this phenotypic chromosomal association and provides further evidence for homogeneity of the TRPS.

Fractionation of large mammalian DNA restriction fragments using vertical pulsed-field gradient gel electrophoresis

A new design for pulsed field gradient (PFG) gel electrophoresis of large (greater than 50 kb) DNA fragments is described. The method eliminates distortion of migration of DNA because of the geometry of the applied electric field, requires a single power supply and a simple switching device, and is extremely simple to use. Parameters investigated include variation in pulse time, conditions of restriction enzyme digestion and DNA concentration, and the use of different restriction endonucleases. The method has been applied to restriction enzyme digested mammalian DNA from Chinese hamster and human/Chinese hamster hybrid sources and has allowed examination of the minimum separation of two DNA markers known to be on the same human chromosome, chromosome 21.

Recently recognized chromosomal defects of clinical importance

We review those conditions which have recently been recognized to be associated with small, sometimes difficult to detect, chromosomal abnormalities. These include the Prader-Willi syndrome and X-linked mental retardation.

Familial syndrome with some features of the Langer-Giedion syndrome, and paracentric inversion of chromosome 8, inv 8 (q11.23----q21.1)

A family is reported with an autosomal dominant inherited syndrome presenting some of the typical features of the tricho-rhino-phalangeal syndrome type II (TRP II) or Langer-Giedion syndrome. The critical region for the expression of the syndrome seems to be at band 8q24.1. In the affected members of the family reported here, anomaly of chromosome 8 was noted, involving however the proximal part of the 8 long arm, which was interpreted as a paracentric inversion. Whether the anomaly is causally or only casually related to the syndrome is a matter of discussion.