Hox genes
• Regula-ng genes • Transcribe transcrip-on factors • Homeo-c genes à important for segmenta-on
Endocrine Reviews June 1, 2006 vol. 27 no. 4 331-‐355
Phenotype Ts/+ mice?
Ts/+: • 18 kb dele-on in gene that encodes
for RPL38 (Ribosomal protein) • heterozygote
àSkeletal paOerning defects!
RPL38
Crystal structure: Proc.Natl Acad Sci USA 2010 Nov 16;107(46):19754-‐9
PaOerning due to altered Hox levels?
• No change in Hox transcrip-on levels (qPCR) • No change in total protein synthesis (in vivo):
Rela-ve transla-on rate of mRNAs?
Same for: Hoxa4 Hoxa9 Hoxa11 Hoxb3 Hoxb13 Hoxc8 Hoxd10
qPCR
Polysome profiling
Biochemistry, Gene0cs and Molecular Biology ISBN 978-‐953-‐51-‐0758-‐3
Molecular step at which RPL38 affects transla-on
RPL38 facilitates 80S complex forma-on for some Hox mRNAs
Consequence: diminished HOX protein levels in Ts/+
qPCR(in somites)
Immunofluoresence
Western Blot
Hoxa5:
Addi-onaly: • restored HOXA5 level in transgenic mice • Ts/+ Hoxa5 mRNAs in vitro translated
Missing subset of Hox mRNAs explains Ts/+ Phenotype
Func-on of RPL38 on or off the ribosome?
Western Blot
Rpl38 transcript enrichement in specific -ssues
In situ hybridisa-on
Summary • Rpl38 transla-onally controls a subset of Hox mRNAs
• Ribosome –mediated transla-onal specifity as a new layer of expression regula-on
• Indica-ons towards specialised Ribosomes
Hoxa5 Hoxa4 Hoxa9 Hoxa11 Hoxb3 Hoxb13 Hoxc8 Hoxd10
No 80S assembly