A recent study by Liu and colleagues identified mutations in TCF20, a paralog of RAI1, among individuals manifesting a novel syndrome that has phenotypes similar to those of Smith-Magenis syndrome (a disorder caused by disruption of RAI1).
TCF20 encodes a transcriptional co-regulator structurally related to RAI1, the dosage-sensitive gene responsible for Smith-Magenis syndrome (deletion/haploinsufficiency) and Potocki-Lupski syndrome (duplication/triplosensitivity).
Together, these results suggest the existence of a postnatal temporal window during which restoring Rai1 can improve the transcriptional and social behavioral deficits in a mouse model of SMS.
About 90% of SMS cases are due to a 17p11.2 deletion containing retinoic acid induced1 (RAI1) gene, 10% are due to heterozygous mutations affecting RAI1 coding region.Little is known about RAI1 role.
Smith-Magenis syndrome (SMS) is a complex genetic disorder caused by interstitial 17p11.2 deletions encompassing multiple genes, including the retinoic acid induced 1 gene-RAI1-or mutations in RAI1 itself.
We investigated a cohort of 15 individuals with a clinical suspicion of SMS who showed neither deletion in the SMS critical region nor damaging variants in RAI1 using whole exome sequencing.
Nonrecurrent PMP22-RAI1 contiguous gene deletions arise from replication-based mechanisms and result in Smith-Magenis syndrome with evident peripheral neuropathy.
Notably, this is the first reported instance of patients with RAI1 missense mutation whose HL is not accompanied by specific traits typical for Smith-Magenis syndrome.
RAI1 (retinoic acid induced-1) is a dosage-sensitive gene that causes Smith-Magenis syndrome (SMS) when mutated or deleted and Potocki-Lupski Syndrome (PTLS) when duplicated, with psychiatric features commonly observed in both syndromes.
Smith‑Magenis syndrome (SMS) is a rare condition with multiple congenital malformations caused by the haploinsufficiency of RAI1 (deletion or mutation of RAI1).
These SMS-like phenotypes are produced by loss of Rai1 function in distinct neuronal types: Rai1 loss in inhibitory neurons or subcortical glutamatergic neurons causes learning deficits, while Rai1 loss in Sim1<sup>+</sup> or SF1<sup>+</sup> cells causes obesity.
Smith-Magenis syndrome (SMS) is a multiple congenital anomalies/mental retardation disorder characterized by an interstitial deletion involving chromosome 17p11.2 containing the retinoic acid-induced 1 (RAI1) gene or due to mutation of RAI1.
As other similar cases may exist, this report will help to increase awareness of the possibility of a very late diagnosis of SMS, with the need for re-evaluation of individuals suspected to have SMS who were initially evaluated prior to the identification of the RAI1 gene.
The chromosome diagnosis revealed an interstitial deletion of 17p11.2 and the diagnosis of the SMS was confirmed.Accurate clinical diagnosis, therapeutic assessments and a holistic management plans, including multidiscipline therapeutic strategies, periodic neuro-developmental assessments, and an early intervention programs, are recommended.However, cytogenetic analysis or FISH using an RAI1-specific probe is the most frequently used technique for DS.
Clinical features of patients with or without 17p11.2 deletions and mutations involving the RAI1 gene were compared to identify phenotypes that may be useful in diagnosing patients with SMS.
Data further show that haploinsufficiency of RAI1 and Rai1 in SMS fibroblasts and the mouse hypothalamus, respectively, results in the transcriptional dysregulation of the circadian clock and causes altered expression and regulation of multiple circadian genes, including PER2, PER3, CRY1, BMAL1, and others.
Our results showed for the first time a correlation between RAI1 mutations and abnormal protein function plus they suggest that a reduction of total RAI1 transcription factor activity is at the heart of the SMS clinical presentation.
Data further show that haploinsufficiency of RAI1 and Rai1 in SMS fibroblasts and the mouse hypothalamus, respectively, results in the transcriptional dysregulation of the circadian clock and causes altered expression and regulation of multiple circadian genes, including PER2, PER3, CRY1, BMAL1, and others.