Human Molecular Genetics, Vol. 1, No. 3 161—164 Characterization of a YAC containing part or all of the Norrie disease locus Z.-Y.Chen, K.B.Sims 2 , M.Coleman 3 , D.Donnai 1 , A.Monaco 3 , X.O.Breakefield 2 , K.E.Davies 3 and I.W.Craig* Genetics Laboratory, Department of Biochemistry, South Parks Road, Oxford, 0X1 3QU, 1 St Mary's Hospital, Hathersage Road, Manchester M13 OJH, UK, 2 Molecular Neurogenetics Laboratory, Neuroscience Centre, Massachusetts General Hospital - East, Building 149, 13th Street, Chariestown, MA 02129, USA and institute of Molecular Medicine, John Radcliffe Hospital, Oxford 0X3 9DU, UK Received April 2, 1992; Revised and Accepted May 6, 1992 ABSTRACT It has been shown from pulsed-field gel electrophoresis (PFGE) that the monoamine oxidase genes A and B (MAOA & MAOB) and DXS7 loci are physically very close. We have therefore extended studies on their relationship through the characterisation of a 650 kb YAC isolated using L1.28 (recognising the DXS7 locus) as a probe. Restriction mapping of the YAC indicates that it contains both MAOA and MAOB genes in addition to the DXS7 locus. The map derived from the YL1.28-YAC is compatible both with the map from an independently derived YAC carrying MAOA and B genes and with the long range genomic map for the region. A series of subclones prepared from a 'phage library (lambda DASH II) of the YAC have been characterised and have been employed to determine the end point of the deletion of a Nome disease (NDP) patient who has been shown to lack both DXS7 and MAO coding sequences. The pattern of retention of subclones in the deletion patient place the end point of the deletion within 30-130 kb of the proximal end of the YAC. By combining the data with established recombination analysis, we provide evidence that all or part of the NDP lies in the interval of approximately 250kb within the YAC. INTRODUCTION Norrie disease (pseudoglioma, NDP) is a severe, X-linked, recessive neurological disorder of unknown pathogenesis and is characterised by congenital blindness, sensory neural deafness and mental retardation. Its localisation to Xpl 1.4-pl 1.3 was established by virtue of its manifestation in patients from a Finnish kindred showing an atypical complex phenotype comprising microcephaly, atonic seizures, myoclonus and somatic growth failure. It was deduced that patients from this kindred had a submicroscopic deletion of the X chromosomal region embracing the disease locus and which included the anonymous DNA locus DXS7 (1) Subsequently, both monoamine oxidase A and B genes (MAOA and MAOB) were shown to be deleted in affected individuals in this kindred resulting in a deficiency for monoamine oxidase enzyme activity (2). Three other atypical Norrie disease patients with submicroscopic deletions, including the DXS7 locus, have been described (3,4,5); all of them lack the MAOA and B genes (6,7; Chen, Z-Y., Powell, J.F. and Craig, I.W.—unpublished data). Physical mapping of the Norrie disease locus in deletion patients has identified a distal flanking marker DXS77, which is recognised by the probe pX59 (8). Recombination has been observed between DXS7 (LI.28) and NDP (9,10); furthermore, additional observations on one of the individuals revealed that no recombination had occurred between the disease locus and the OAT complex—which is physically located proximal to DXS7 (11). It was therefore suggested that NDP lies proximal to DXS7. This information has been recently extended by the demonstration by Lindsay et al (12) that the cross- over is also distal to the microsatellite marker, DXS426, which maps proximal to DXS7 at Xpl 1.4-pl 1.23, suggesting the order tel_DXS7_NDP_DXS426_cen. Because of the close proximity between DXS7, MAOA, MAOB and Norrie disease, we have undertaken a detailed investigation of the physical map in the region. This analysis, together with further analysis of a Norrie patient with a deletion and additional recombination data now available, has enabled us to determine that sequences important in the manifestation of Norrie disease are localized to an interval of about 250kb within a YAC of total size 650kb. RESULTS The 650kb YAC we studied was obtained by screening a 48, XXXX YAC library (16) for the locus DXS7 (see Methods Section); it is designated YL1.28. Detailed restriction mapping of the YAC indicates that it contains both MAOA and MAOB genes in addition to the DXS7 locus (see Figure 1). DXS7 was mapped to a 30kb Clal fragment, at the left end of the YAC. DXS7 and MAO genes are on adjacent Sfil fragments within the YAC and separated by about 140 kb. MAOA and MAOB genes are found in a tail-to-tail configuration with the 3' coding sequences separated by about 40kb. The map derived from the YL1.28-YAC is compatible both with the information obtained with an independent YAC isolated with MAOA and the long range genomic map for the region (13). * To whom correspondence should be addressed at Tufts University on December 28, 2012 http://hmg.oxfordjournals.org/ Downloaded from