Genomic organization of the mouse gene for lung surfactant protein D

Lung surfactant protein (SP)-D belongs to the family of soluble collagenous C-type lectins, named collectins, SP-D participates in the local innate im mune defense of the lung, eliciting various effector functions by acting as a pattern recognition receptor for the carbohydrate structures on inhaled microorganisms and particulate matter. This work describes the isolation an d characterization of the mouse SP-D gene (Sftpd), which spans 8 exons over 14 kb of sequence and shows an overall organization similar to other colle ctin genes. The complete 5' untranslated region of the messenger RNA, absen t from the published complementary DNA for mouse SP-D, was also cloned and is shown to be encoded by a single exon. Analysis of 3.5 kb of 5' flanking nucleotide sequence for Sftpd is described and reveals positional conservat ion of a number of transcription factor binding sites on comparison of Sftp d with the human SP-D gene and the bovine conglutinin gene. In addition, a single copy SP-D-like gene has been shown to be present in mammals, birds, and amphibians but is absent in fish. An atypical, rodent-specific, long te rminal repeat of retroviral origin containing a minisatellite that has beco me inserted in Sftpd is described. Three new polymorphic microsatellites ar e also described, one of which is just 160 base pairs upstream of Sftpd. Th is microsatellite was used to map the gene to the central region of chromos ome 14; fine-scale mapping indicates that it lies in a 5.64-centimorgan are a between D14Mit45 and D14Mit60. This will allow the easy identification of the collectin gene cluster and aid in the construction of a physical map o ver this region.