Israel Medical Association Journal

Background: Nail-patella syndrome (NPS) is characterized by changes in the nails, knees, and elbows, as well as the presence of iliac horns detected by X-ray of the pelvis. A higher occurrence of psychiatric disorders has also been suggested in NPS. Heterozygous mutations in the gene encoding the LIM-homeodomain transcription factor (LMX1B) are identified in most patients with typical clinical findings of NPS.

Objective: To report on the association between NPS and schizophrenia.

Methods: Genomic DNA were isolated from a patient's venous blood and collected on ethylenediaminetetraacetic 5% with the Gentra Puregene Blood Kit. All exons and flanking regions of the LMX1B gene (LMX1B: NM_001174146.1) were amplified by standard polymerase chain reaction and analyzed by direct DNA sequencing with BigDye Terminators on an ABI 3100 sequencer. Sequence chromatograms were analyzed using SeqScape software version 1.1. Mutation analysis and characterization of variants was performed with the Alamut Software Version 2.1.

Results: We report a patient presenting to the psychiatry department with schizophrenia. Clinical examination revealed characteristic findings consistent with NPS. Since NPS was suspected, based on clinical findings, sequencing of all coding exons of LMX1B gene was completed. Results revealed a novel heterozygous mutation in the proband: c.546_547insACCG(het); p.Glu183Thrfs*11.

Conclusions: Based on LMX1B expression in brain regions that are implicated in neuropsychiatric illness, and especially in the development of dopaminergic neurons, we hypothesize that schizophrenia may be part of the clinical spectrum of NPS.

The ubiquitin-proteasome pathway has a central role in selective degradation of intracellular proteins. Among the key proteins degraded by the system are those involved in the control of inflammation, cell cycle regulation and gene expression. With numerous important cellular pathways affected, derangements in the ubiquitin system were shown to result in a variety of human diseases including malignancies, neurodegenerative diseases and hereditary syndromes, and proteasome inhibition was implicated as a potential treatment for cancer and inflammatory conditions. Two proteasome inhibitors are currently under clinical evaluation for multiple myeloma and acute ischemic stroke. The ubiquitin system also has an important function in the immune and inflammatory response. It is involved in antigen processing and presentation to cytotoxic T cells, and the activation of nuclear factor-kappa B – the central transcription factor of the immune system. Since the proteasome is the central source of antigenic peptides that are presented to the immune system, some viruses, such as the Epstein-Barr virus, developed escape mechanisms that manipulate the ubiquitin-proteasome system in order to persist in the infected host. Understanding the mechanisms underlying the production of viral antigens by the ubiquitin-proteasome system may have therapeutic applications such as future development of vaccines.