ABSTRACT
Mitchell-Riley syndrome (MRS) is caused by recessive mutations in the regulatory factor X6 gene (RFX6) and is characterised by pancreatic hypoplasia and neonatal diabetes. To determine why individuals with MRS specifically lack pancreatic endocrine cells, we micro-CT imaged a 12-week-old foetus homozygous for the nonsense mutation RFX6 c.1129C>T, which revealed loss of the pancreas body and tail. From this foetus, we derived iPSCs and show that differentiation of these cells in vitro proceeds normally until generation of pancreatic endoderm, which is significantly reduced. We additionally generated an RFX6HA reporter allele by gene targeting in wild-type H9 cells to precisely define RFX6 expression and in parallel performed in situ hybridisation for RFX6 in the dorsal pancreatic bud of a Carnegie stage 14 human embryo. Both in vitro and in vivo, we find that RFX6 specifically labels a subset of PDX1-expressing pancreatic endoderm. In summary, RFX6 is essential for efficient differentiation of pancreatic endoderm, and its absence in individuals with MRS specifically impairs formation of endocrine cells of the pancreas head and tail.
Subject(s)
Cell Differentiation , Diabetes Mellitus/genetics , Diabetes Mellitus/pathology , Endoderm/embryology , Gallbladder Diseases/genetics , Gallbladder Diseases/pathology , Induced Pluripotent Stem Cells/pathology , Intestinal Atresia/genetics , Intestinal Atresia/pathology , Mutation/genetics , Pancreas/embryology , Regulatory Factor X Transcription Factors/genetics , Alleles , Base Sequence , Cell Differentiation/genetics , Chromatin/metabolism , Consanguinity , Diabetes Mellitus/diagnostic imaging , Embryo, Mammalian/metabolism , Embryonic Development , Family , Female , Gallbladder Diseases/diagnostic imaging , Genome, Human , Humans , Induced Pluripotent Stem Cells/metabolism , Intestinal Atresia/diagnostic imaging , Male , Pedigree , Transcription, Genetic , Transcriptome/genetics , X-Ray MicrotomographyABSTRACT
STATEMENT OF PROBLEM: The tissue surrounding craniofacial implants is prone to inflammation; however, no adequate instrument is currently available to measure this objectively. PURPOSE: The purpose of this study was to describe the parameters influencing the sulcus fluid flow rate in the extraoral periimplant tissue environment. MATERIAL AND METHODS: Thirty-four patients with 112 craniofacial implants participated. The sulcus fluid flow rate (SFFR) was measured with standardized paper strips. The influence of cleansing liquids, implant location, presence of purulent exudates, smoking habits, depth of crevice, and previous irradiation on the sulcus fluid flow rate were evaluated with covariate adjusted finite mixture models. RESULTS: Two latent subgroups of SFFR were identified based on a mixed model. The majority (95.5%) had a mean value of 1.44 mm, and the smaller subgroup (4.5%) had a mean value of 10.4 mm. The SFFR values were increased when purulent exudates were present (regression coefficient 1.41), 95% CI (0.67, 2.16). The depth of the crevice influenced the SFFR per unit depth (regression coefficient 0.37), 95% CI (0.22, 0.53). Additional covariates, such as the implant location, history of smoking, and prior irradiation, had no statistical effect on SFFR. CONCLUSIONS: SFFR can be measured objectively in the extraoral periimplant tissue.
