Mid-facial developmental defects caused by the widely used LacZ reporter gene when expressed in neural crest-derived cells

Abstract

Reporter genes play important roles in transgenic research. LacZ is a widely used reporter gene that encodes Escherichia coli β-galactosidase, an enzyme that is well known for its ability to hydrolyze X-gal into a blue product. It is unknown whether transgenic LacZ has any adverse effects. R26R reporter mice, containing a LacZ reporter gene, were generated to monitor the in vivo recombination activity of various transgenic Cre recombinase via X-gal staining. P0-Cre is expressed in neural crest-derived cells, which give rise to the majority of the craniofacial bones. Herein, we report that 12% of the R26R reporter mice harboring P0-Cre had unexpected mid-facial developmental defects manifested by the asymmetrical growth of some facial bones, thus resulting in tilted mid-facial structure, shorter skull length, and malocclusion. Histological examination showed a disorganization of the frontomaxillary suture, which may at least partly explain the morphological defect in affected transgenic mice. Our data calls for the consideration of the potential in vivo adverse effects caused by transgenic β-galactosidase.

Cranial Neural Crest Specific Deletion of Alpl (TNAP) via P0-Cre Causes Abnormal Chondrocyte Maturation and Deficient Cranial Base Growth

“…This indicates that TNAP is not essential for cranial base development until after birth. While the SOS still contains cells derived from neural crest and mesoderm at birth, previous reports showed the rostral movement of the neural crest/mesoderm boundary during postnatal cranial base development, leading ultimately to an SOS composed ultimately of mesoderm-derived cells at day 10 postnatal when labeled using a Wnt1-Cre driver [5], and at day 7 post birth, when labeled using a Po-Cre driver [6]. Consistent with the above findings that the SOS develops into a tissue of entirely mesoderm origin after birth, our results showed thebcomplete elimination of Alpl in the prehypertrophic and hypertrophic zones of the ISS but not the SOS of 5-day-old Alpl fl/fl ; P0-Cre + mice via TNAP enzyme activity staining (Figure 3A), indicating that no cells of the SOS expressed P0 and so were mesoderm-derived at this time point.…”

“…The spheno-occipital synchondrosis (SOS) is initially derived from a mixed neural crest and paraxial mesoderm origin, while the intersphenoid synchondrosis (ISS) is of cranial neural crest origin [5]. During postnatal development, the mesoderm/neural crest boundary within the SOS migrates rostrally such that the SOS becomes solely of mesoderm origin by several days after birth [5,6]. The abnormal development and premature fusion of cranial base synchondroses is associated with numerous genetic disorders, leading to the deficient anterior-posterior growth of the skull, associated skull shape defects and malocclusion (teeth not fitting together appropriately).…”