Smith-Magenis syndrome (SMS) is a genetic neurodevelopmental disease characterized by neurological, psychiatric, anatomical, and motor symptoms. The disease is caused by deletions on chromosome 17p11.2, which may lead to the loss of up to 95 genes, depending on the length of the chromosomal rearrangement. One of these genes is retinoic acid-induced 1 (RAI1). Evidence that loss of RAI1 is responsible for several clinical manifestations of SMS came with the identification of patients carrying point mutations in this gene and presenting a phenotype overlapping with SMS. Rather, disease severity and some clinical presentations are associated with loss of genes other than RAI1. SMS patients are typically heterozygous for the mutation (RAI1 mutations and chromosomal deletions), indicating that loss of one functional allele of RAI1 is sufficient to cause disease. Interestingly, duplications of the same chromosomal region cause another neurodevelopmental disease with similar clinical manifestations, thus indicating that RAI1 (and possibly other genes nearby) are dosage-sensitive genes. RAI1 is a polyglutamine- and polyserine-containing factor induced by retinoic acid and with nuclear localization. However, its function in physiological conditions and how its haploinsufficiency causes SMS is not known. Here, we will review several aspects related to SMS, from diagnosis to clinical presentation. Moreover, we analyze in detail what is known about the RAI1 isoforms, expression pattern, native function, and the impact of different types of mutations (deletions, frameshift mutations that generate premature stop codons, and missense mutations that result in the production of the full-length protein). Finally, we review the animal and cell models available to date, focusing on those based on the immortalized pluripotent technology. These patient-derived cells allow replicate in a dish an otherwise irreproducible condition, which takes into account the genetic variability of patients and that may then complement mechanistic studies performed in mouse models of SMS.
Pennuto, M., Sireno, L., Turco, E., Rosati, J., Vescovi, A., Bernardini, L., et al. (2022). Induced pluripotent stem cells for modeling Smith-Magenis syndrome. In A. Birbrair (a cura di), Current Progress in iPSC Disease Modeling A volume in Advances in Stem Cell Biology (pp. 217-246). Elsevier [10.1016/B978-0-323-85765-9.00013-8].
Induced pluripotent stem cells for modeling Smith-Magenis syndrome
Vescovi A. L.;
2022
Abstract
Smith-Magenis syndrome (SMS) is a genetic neurodevelopmental disease characterized by neurological, psychiatric, anatomical, and motor symptoms. The disease is caused by deletions on chromosome 17p11.2, which may lead to the loss of up to 95 genes, depending on the length of the chromosomal rearrangement. One of these genes is retinoic acid-induced 1 (RAI1). Evidence that loss of RAI1 is responsible for several clinical manifestations of SMS came with the identification of patients carrying point mutations in this gene and presenting a phenotype overlapping with SMS. Rather, disease severity and some clinical presentations are associated with loss of genes other than RAI1. SMS patients are typically heterozygous for the mutation (RAI1 mutations and chromosomal deletions), indicating that loss of one functional allele of RAI1 is sufficient to cause disease. Interestingly, duplications of the same chromosomal region cause another neurodevelopmental disease with similar clinical manifestations, thus indicating that RAI1 (and possibly other genes nearby) are dosage-sensitive genes. RAI1 is a polyglutamine- and polyserine-containing factor induced by retinoic acid and with nuclear localization. However, its function in physiological conditions and how its haploinsufficiency causes SMS is not known. Here, we will review several aspects related to SMS, from diagnosis to clinical presentation. Moreover, we analyze in detail what is known about the RAI1 isoforms, expression pattern, native function, and the impact of different types of mutations (deletions, frameshift mutations that generate premature stop codons, and missense mutations that result in the production of the full-length protein). Finally, we review the animal and cell models available to date, focusing on those based on the immortalized pluripotent technology. These patient-derived cells allow replicate in a dish an otherwise irreproducible condition, which takes into account the genetic variability of patients and that may then complement mechanistic studies performed in mouse models of SMS.
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