Do Genetic Alterations in Sex Steroid Receptors Contribute to Lacrimal Gland Disease in Sjögren's Syndrome?

Abstract

BACKGROUND: Defects in sex steroid receptors have been linked to the onset, progression and severity, as well as the sex-related prevalence, of a variety of autoimmune disorders, including lupus, rheumatoid arthritis, multiple sclerosis and diabetes. We hypothesize that defects in estrogen receptor alpha (ESR1), estrogen receptor beta (ESR2) and/or the androgen receptor (AR) may also contribute to the development of lacrimal gland autoimmune sequelae in Sjögren's syndrome. To begin to test this hypothesis, we examined whether mutations exist in the coding regions of ESR1, ESR2 and AR transcripts in lacrimal tissues of mouse models of Sjögren's syndrome. METHODS: Lacrimal and submandibular glands were collected from adult MRL/MpJ-Tnfrsf6(lpr), nonobese diabetic and/or BALB/c mice. Tissues were pooled according to sex and experiment and processed for cDNA generation. PCR primers were designed to amplify 566-875 base pair segments of the entire open reading frame of each receptor. Segments were amplified, purified and then sequenced. Receptor sequences were assembled and compared to each other and to known NCBI sequences. RESULTS: Our results show that almost all ESR1, ESR2 and AR sequences in exocrine tissues of male and female autoimmune and non-autoimmune mice were identical to those of NCBI standards. There was a G-->A shift at position 998 of the ESR2 complete coding sequence in all tissue samples when compared to NCBI reference sequence U81451.1, but this polymorphism was not found in other ESR2 reference sequences. CONCLUSIONS: Our findings indicate that defects in the coding region of sex steroid receptors do not contribute to the pathogenesis of lacrimal gland disease in mouse models of Sjögren's syndrome.

Fig. (1)

Amplicon sizes for each of the sex hormone receptors. Abbreviations are defined in the legend to Table 1.

Fig. (2)

Examples of AR, ESR1 and ESR2 sequences in lacrimal glands of male (M) and female (F) autoimmune and non-autoimmune mice. Images are from the bioanalyzer and molecular weight standards were run in lane “L.” Domain abbreviations are reported in the Table 1 legend, and anticipated band sizes are shown in Fig. (2). The sizing accuracy is ± 10%.

Fig. (3)

Alignment of NOD ESR1 sequences to an NCBI wild type reference sequence. Each number (i.e. 1, 2, 3) represents a different experimental sample. Each sample originated from the lacrimal glands of 5 mice.

Fig. (4)

Alignment of ESR2 sequences to an NCBI wild type reference sequence. All samples were from lacrimal glands (LG), except for those originating from submandibular glands (SMG).