Lowry Wood Syndrome, Microcephalic Osteodysplastic Primordial Dwarfism Types I and III, Roifman Syndrome, Taybi Linder Syndrome
Conditions
Keywords
Genetic diseases, Splicing, Minor introns, U4atac, Primary cillium
Brief summary
In the human genome, about 750 genes contain one intron excised by the minor spliceosome. These genes are named U12 genes, and these introns, minor or U12 introns. The minor spliceosome comprises its own set of snRNAs, among which U4atac. Its non-coding gene, RNU4ATAC, has been found mutated in Taybi-Linder (TALS), Roifman (RFMN) and Lowry-Wood syndromes (LWS). These rare developmental disorders associate ante- and post-natal growth retardation, microcephaly, skeletal dysplasia, intellectual disability, retinal dystrophy and immunodeficiency. Their physiopathological mechanisms remain unsolved: the number of U12 genes involved, their identity and function, or the cellular mechanisms impacted by the splicing defect, are still unknown. The hypothesis of the study is that U12 genes coding for primary cilia components are particularly sensitive to minor splicing defects caused by RNU4ATAC mutations. Indeed, a child showing signs of TALS but negative for RNU4ATAC was found to carry a homozygous variant in the RTTN gene, coding for the rotatin protein located at the centrosome and the base of the primary cilia and playing a role in maintaining these structures. In addition, bi-allelic RNU4ATAC mutations were identified in five patients presenting with traits suggestive of the Joubert syndrome (JBTS), a well-characterized ciliopathy. These patients also present with traits typical of TALS/RFMN/LWS. To better understand the causes of these pathologies, a cohort of patients with syndromes associated with bi-allele mutations of the RNU4ATAC or RTTN gene will be gathered, in order to conduct studies on the cells of these patients. Blood samples will be taken, as well as skin biopsies, if possible. These samples will be used to create induced pluripotent stem cell lines. Blood samples will also be collected from the parents of RNU4ATAC patients, to eliminate in transcriptomic analyses expression variations due to differences in genetic background. Biopsies of skin, muscle and brain tissue will be collected on foetuses carrying two-allele RNU4ATAC or RTTN mutations whose parents have had a miscarriage or have chosen to have a medical abortion. The biological samples collected will be used to study the transcription level of U12 genes, the splicing of their pre-messenger RNA, their main cellular functions, and the structural characteristics of tissues and cells.
Interventions
OTHERBlood samples
Blood samples of 5 ml to 15 ml depending on their weight
OTHERSkin biopsies
Biopsies of fragment of skin 2 to 3 mm long by 1 mm wide and 1 mm deep will preferably be taken on the inside of the arm, in the upper third, between the bend of the elbow and the hollow of the armpit under strict sterility conditions.
OTHERFetal samples
Skin, muscle, brain and bone biopsies will be collected from fetuses in the autopsy room after the medical termination of pregnancy or miscarriage
Sponsors
Hospices Civils de Lyon
Study design
Allocation
NON_RANDOMIZED
Intervention model
SINGLE_GROUP
Primary purpose
OTHER
Masking
NONE
Eligibility
Sex/Gender
ALL
Healthy volunteers
Yes
Inclusion criteria
TALS, RFMN, LWS or other pathology patients * Woman or man * All ages * Presence of bi-allelic mutations of RNU4ATAC or RTTN * Written consent of parents or legal guardian(s) * Affiliation to a Social Security scheme Healthy participants (Parent of the patient) * Woman or man * Major * Presence of mono-allelic mutations of RNU4ATAC * Written consent of the participant * Affiliation to a Social Security scheme Parents having recourse to a medical termination of pregnancy or having had a spontaneous miscarriage (for fetus samples) * Woman or man * Major * Presence of bi-allelic mutations of RNU4ATAC or RTTN in the fetus * Written parental consent * Affiliation to a Social Security scheme
Exclusion criteria
Subject participating in another research including an exclusion period still in progress.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Identification of RNU4ATAC mutations consequences at the cellular level | 5 years | The dysfunctions present in the different cell types obtained from RNU4ATAC patients will be identified by comparison with the controls, and will be compared with those present in RTTN patients. Consequences in cells of patients of RNU4ATAC mutations on the length and the structure of the primary cilium, as measured by fluorescence microscopy, and on the formation of small nuclear ribonucleoprotein (snRNPs) particles, as measured by glycerol gradient sedimentation analysis |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Minor splicing anomalies | 5 years | The number and list of U12 genes for which an alteration of splicing will be identified in patient cells relatively to control cells will be compared, taking into account the different phenotypes (TALS, RFMN, LWS and other pathologies possibly identified). Consequences in cells of patients of RNU4ATAC mutations on minor intron splicing, as measured by intron retention analysis with the IRFinder and KisSplice bioinformatics softwares following RNA-sequencing experiments |
| Understanding of neuronal differentiation anomalies | 5 years | Abnormalities in the behaviour of cells differentiated into neuronal progenitors will be identified by comparison with the controls, and will be compared taking into account the different phenotypes (TALS, RFMN, LWS and other pathology(s)) possibly identified). Consequences of RNU4ATAC mutations on the ability of induced pluripotent stem cells to differentiate towards the neuronal lineage, as measured by immunocytochemistry |
Countries
France
Contacts
Primary ContactSylvie MAZOYER, Dr
Backup ContactPatrick EDERY, Pr
Outcome results
None listed