Smith-Magenis (RAI1) and Miller-Dieker (LIS1) Probe Combination

RAI1 (SMCR 17p11.2): Green
LIS1 (MDS/ILS 17p13.3): Red

Smith-Magenis syndrome (SMS) is a multiple congenital anomaly syndrome characterised by mental retardation, neuro-behavorial abnormalities, sleep disturbances, short stature, minor craniofacial and skeletal anomalies, congenital heart defects and renal anomalies. It is one of the most frequently observed human microdeletion syndromes and associated with an interstitial deletion of the chromosome band 17p11.2.

Molecular studies in SMS patients suggest a common deletion region spanning approximately 700 kb of the chromosome. One gene in this region, RAI1 (retinoic acid induced 1) has been shown to be the primary gene responsible for most features of SMS so Cytocell has updated its existing SMS/MDS probe product to reflect this new scientific finding. The new probe is placed within this 700Kb common deleted region and encompasses the distal half of RA1 Miller-Dieker syndrome (MDS) is a multiple malformation characterised by classical lissencephaly, a characteristic facial appearance and sometimes other birth defects. Isolated lissencephaly sequence (ILS) consists of classical lissencephaly with no other major anomalies.

Visible or submicroscopic rearrangements within chromosome band 17p13.3 occur in almost all cases of MDS and in almost 40% of ILS patients. MDS is considered a contiguous gene deletion syndrome, resulting in a deleted region which includes LIS1. This gene is found to be deleted in both syndromes so Cytocell’s MDS probe will detect both MDS and ILS as it is a 90 kb probe which covers the entire LIS1 gene. The SMS/MDS combined product therefore provides two tests in one, in common with some of these other new products. The MDS probe thus acts as a control for SMS diagnosis and the SMS probe acts as a control for the diagnosis of MDS, a completely separate syndrome on the same chromosome: two products in one.