Beckwith-Wiedemann-like macroglossia and 18q23 haploinsufficiency.

Beckwith-Wiedemann syndrome (BWS) is an overgrowth condition with tumor proclivity linked to a genetic imbalance of a complex imprinted region in 11p15.5. A female child with features fitting in with the BWS diagnostic framework and an apparent loss of imprinting (LOI) of the IGF2 gene in 11p15.

FRA18C: a new aphidicolin-inducible fragile site on chromosome 18q22, possibly associated with in vivo chromosome breakage.

Fragile sites are specific genomic loci that form gaps, constrictions and breaks on chromosomes exposed to replication stress conditions. In the father of a patient with Beckwith-Wiedemann syndrome and a pure truncation of 18q22-qter, a new aphidicolin-sensitive fragile site on chromosome 18q22.2 (FRA18C) is described.

The reduced expression of the HADH2 protein causes X-linked mental retardation, choreoathetosis, and abnormal behavior.

Recently, we defined a new syndromic form of X-linked mental retardation in a 4-generation family with a unique clinical phenotype characterized by mild mental retardation, choreoathetosis, and abnormal behavior (MRXS10). Linkage analysis in this family revealed a candidate region of 13.4 Mb between markers DXS1201 and DXS991 on Xp11; therefore, mutation analysis was performed by direct sequencing in most of the 135 annotated genes located in the region.

CGG-repeat expansion in the DIP2B gene is associated with the fragile site FRA12A on chromosome 12q13.1.

A high level of cytogenetic expression of the rare folate-sensitive fragile site FRA12A is significantly associated with mental retardation. Here, we identify an elongated polymorphic CGG repeat as the molecular basis of FRA12A. This repeat is in the 5' untranslated region of the gene DIP2B, which encodes a protein with a DMAP1-binding domain, which suggests a role in DNA methylation machinery.

Identification of a family with nonspecific mental retardation (MRX79) with the A140V mutation in the MECP2 gene: is there a need for routine screening?

Mutations in the methyl-CpG-binding protein 2 (MECP2) cause Rett syndrome, a severe neurodevelopmental disorder occurring predominantly in females. Male patients with Rett syndrome are extremely rare, as the Rett-causing mutations in the MECP2 gene are usually lethal in hemizygous males. However, different mutations in the same gene were reported to cause mental retardation, both in sporadic non-syndromic males as well as in syndromic families with disease manifestation in carrier females.

Family MRX9 revisited: further evidence for locus heterogeneity in MRX.

Nonspecific X-linked mental retardation (MRX) patients are characterized by mental retardation, without additional distinguishing features. Consequently, MRX families can only be distinguished by mapping studies; yet, due to imprecise mapping studies performed in the past, the number of genes causing MRX is debatable, and a more precise localization for families is necessary to estimate this number. MRX 9 has been mapped to the pericentromeric region Xp21-q13.

RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) AND PARSIMONY METHODS.

- Random amplified polymorphic DNA (RAPD) data possess a number of undesirable features for parsimony analysis. These features include their non-codominant inheritance, their anonymous nature, their different (a)symmetrical transformation probabilities, and their possible GC priming bias. As a consequence, no single parsimony method seems appropriate for RAPD data.

CLADISTIC ANALYSIS OF METAZOAN RELATIONSHIPS: A REAPPRAISAL.

Abstract- A recently published cladistic analysis of metazoan relationships based on 77 embryological and morphological characters is shown to be defective with respect to both methodological issues and the interpretation of certain characters. Consequently, many conclusions of this analysis are not supported by the data. Alternative phylogenetic hypotheses are therefore proposed, based on a re-evaluation of an adapted data set.