SPINE Volume 28, Number 17, pp 2025–2029 ©2003, Lippincott Williams & Wilkins, Inc. Allelic Variants of Human Melatonin 1A Receptor in Patients with Familial Adolescent Idiopathic Scoliosis Jose A. Morcuende, MD, PhD,* Raman Minhas, PhD(c),† Lori Dolan, PhD(c),* Jeff Stevens, PhD,* John Beck, BS,† Kai Wang, PhD,‡ Stuart L. Weinstein, MD,* and Val Sheffield, MD, PhD† Study Design. A genetic study of patients with familial adolescent idiopathic scoliosis. Objectives. The purpose of this study was to evaluate the evidence for linkage on chromosome 4q and deter- mine whether mutations in the gene coding for melatonin receptor are present. Summary of Background Data. Adolescent idiopathic scoliosis is the most common spine deformity arising during childhood, but its cause remains unknown. The fact that adolescent idiopathic scoliosis is often seen in several members of the same family strongly suggests a genetic factor. Recent work by Wise et al provides evi- dence for linkage of adolescent idiopathic scoliosis at several different chromosome sites, including 4q. In ad- dition, there is some evidence that adolescent idiopathic scoliosis may be related to a disturbance in melatonin metabolism, and the human melatonin-1A receptor is known to be located on chromosome 4q. Methods. Probands having clinically relevant idiopathic scoliosis (Cobb angle 30°) and their relatives were identi- fied. Radiographic confirmation was required for a positive diagnosis. Linkage analysis was performed with 15 micro- satellite markers of chromosome 4q spaced at approxi- mately 10-cM resolution and 5 microsatellite markers sur- rounding the site for human melatonin receptor. The gene for human melatonin receptor was screened for mutations in the coding region using genomic DNA samples by single- strand conformational polymorphism analysis. Amplimers showing a band shift were reamplified and sequenced bidirectionally. Results. There was no evidence for linkage at chromo- some 4q in this study population. Twenty-nine individuals demonstrated aberrant single-strand conformation poly- morphism band patterns, and sequence evaluation dem- onstrated six genetic polymorphisms for the gene for human melatonin receptor. These genetic variations were found in both affected and nonaffected individuals, and there was no correlation between gene variants and the phenotype for adolescent idiopathic scoliosis. Conclusions. The results of this study demonstrated no evidence of linkage to chromosome 4q and no muta- tions in the coding region of the gene for human melato- nin receptor. The identification of variants in the human melatonin receptor could provide a useful tool for testing the gene in the predisposition to various other melatonin- related disorders and for clarifying the role of melatonin in adolescent idiopathic scoliosis. [Key words: etiology, genetics, adolescent idiopathic scoliosis, melatonin, hMel-1A receptor] Spine 2003;28:2025–2029 Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity arising during childhood. It is characterized by a complex curvature of the spine in the absence of any congenital, neurologic, or musculoskele- tal condition. Using 10° as the minimal degree of curva- ture required to make the diagnosis, the prevalence of this condition in the at-risk population (children 10 –16 years of age) is approximately 2 to 3%, and a curvature that requires treatment will likely develop in about 2 per 1000 individuals (with females predominating by a ratio of 10:1). Although AIS is not life-threatening in the short term, its treatment is long, difficult, and expensive and can be associated with considerable morbidity and com- plications. Despite extensive clinical and basic research, the cause of AIS is unknown. 1 The fact that AIS is often seen in multiple members of the same family strongly suggests a genetic factor in the cause of this condition. 2–24 Recent work by Wise et al provides evidence for linkage of AIS at chromosomes 6p, distal 10q, 4q, and 18q with maximum nonparametric lod scores of 1.42 (P = 0.02), 2.55 (P = 0.033), 5.08 (P = 0.015), and 6.33 (P = 0.002), respectively. 22,23 The authors concluded the data suggest a limited number of loci predisposing to familial AIS. Interestingly, experimental pinealectomy in newborn chickens leads to a spinal deformity similar to idiopathic scoliosis in humans. 25–33 It has been suggested that a deficiency in melatonin, the main product of the pineal gland, is responsible for this deformity, because both autografting of the pineal gland and administration of melatonin prevented the development of scoliosis in this animal model. The lack of melatonin may be the respon- sible factor in this model, but it is also possible that mutations on its receptors could be the causative factor. In mammals, two subtypes of melatonin receptors have been isolated: melatonin-1A (hMel-1A) and melatonin 1B (hMel-1B) receptors. The gene for hMel-1A is located on chromosome 4q, which, when it is considered that the From the Departments of *Orthopaedic Surgery, †Pediatrics, and ‡Biostatistics, University of Iowa, Iowa City, Iowa, USA Supported by research grants from the Pediatric Orthopaedic Society of North America, the Orthopaedic Research and Education Foundation, the Children’s Miracle Network, and the Libbie-Pink Foundation. The manuscript submitted does not contain information about medical device(s)/drug(s). Foundation funds were received in support of this work. No benefits in any form have been or will be received from a com- mercial party related directly or indirectly to the subject of this manuscript. Acknowledgment date: October 15, 2002. Acceptance date: December 18, 2002. Address reprint requests to Jose A. Morcuende, MD, PhD, Department of Orthopaedic Surgery, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, IA City, IA 52242. E-mail: jose-morcuende@uiowa.edu 2025