LETTER TO JMG

A new MRXS locus maps to the X chromosome pericentromeric region: a new syndrome or narrow definition of Sutherland-Haan genetic locus?

M Fichera¹, E Borgione¹, E Avola², S Amata¹, M Sturnio¹, C Romano², A Ragusa¹

¹ Laboratorio di Patologia Genetica, IRCCS Oasi Maria SS, Troina (EN), Italy
² Unità Operativa di Pediatria, IRCCS Oasi Maria SS, Troina (EN), Italy

Correspondence to:
Correspondence to:
Dr A Ragusa, Laboratorio di Patologia Genetica, IRCCS Oasi Maria SS, via Conte Ruggero 73, 94018 Troina (EN), Italy;
angela.ragusa@oasi.en.it

Keywords: X linked mental retardation; MRXS locus; Sutherland-Haan syndrome

Abbreviations: MR, mental retardation; XLMR, X linked mental retardation; MRXS, syndromal X linked mental retardation; MRX, non-specific X linked mental retardation; SHS, Sutherland-Haan syndrome; AR androgen receptor; RENS1, Renpenning syndrome

X linked mental retardation (XLMR) is classically divided into syndromal (MRXS) and non-specific (MRX) forms, depending on the presence or absence of specific distinguishing clinical, morphological, neurological, or metabolic anomalies. In the last XLMR update¹ (http:/xlmr.interfree.it), genetic loci have been assigned for 117 of 202 XLMR by linkage studies, of which only 33 genes have been cloned. From these data, several forms of both syndromal (MRXS) and non-specific mental retardation (MRX) remain without a gene(s) associated disease.¹ Moreover, several allelic disorders have been described for some individual cloned genes, reflecting the heterogeneous functional role of a single XLMR associated gene. For instance, molecular defects on the zinc finger/helicase XNP/ATR-X gene,^{2, 3} the proteolipid protein (PLP), ⁴ and neuronal cell adhesion molecule L1⁵ (MIM 308840) have been associated with distinct clinical entities. Recently, the MECP2 gene (MIM 300005) responsible for Rett syndrome (MIM 312750) has been shown to account . . . [Full text of this article]

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