Study of the Pathophysiology of RNU4ATAC and RTTN Associated Syndromes

Not Applicable

Recruiting

• Conditions: Lowry Wood Syndrome; Taybi Linder Syndrome; Microcephalic Osteodysplastic Primordial Dwarfism Types I and III; Roifman Syndrome
• Interventions: Other: Fetal samples; Other: Blood samples; Other: Skin biopsies

• Registration Number: NCT06111950
• Lead Sponsor: Hospices Civils de Lyon

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.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2023-03-31
• Study First Submitted QC: 2023-10-26
• Study First Posted: 2023-11-01
• Study Start: 2024-08-27
• Status Verified: 2024-10
• Last Update Submitted: 2024-10-08
• Last Update Posted: 2024-10-09
• Primary Completion: 2029-08-27
• Study Completion: 2029-08-27

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 45

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.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
RNU4ATAC fetus	Fetal samples	Fetus with bi-allelic mutation of the RNU4ATAC gene
RTTN patient	Blood samples	Patient with bi-allelic mutation of the RTTN gene
RNU4ATAC patient	Blood samples	Patient with bi-allelic mutation of the RNU4ATAC gene
RNU4ATAC patient	Skin biopsies	Patient with bi-allelic mutation of the RNU4ATAC gene
RNU4ATAC parent	Blood samples	Parent of patient or fetus with bi-allelic mutation of the RNU4ATAC gene and who present themselve mono-allelic mutation of the RNU4ATAC gene
RTTN patient	Skin biopsies	Patient with bi-allelic mutation of the RTTN gene
RTTN fetus	Fetal samples	Fetus with bi-allelic mutation of the RTTN gene

Primary Outcome Measures

Name	Time	Method
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 Outcome Measures

Name	Time	Method
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

Trial Locations

Locations (6)

Centre de référence des anomalies du développement et syndromes malformatifs du Sud-Ouest Occitanie Réunion, CHU de Bordeaux-GH Pellegrin; 🇫🇷 Bordeaux, France

Centre de référence anomalies du développement de Lyon, Hôpital Femme Mère Enfant; 🇫🇷 Bron, France

Centre de référence des anomalies du développement et syndromes malformatifs de l'Est, CHU de DIJON; 🇫🇷 Dijon, France

Centre de référence des anomalies du développement et syndromes malformatifs de l'inter région Nord-Ouest, Hôpital J de Flandre; 🇫🇷 Lille, France

Unité Fonctionelle d'embryo-fœtopathologie, Hôpital Necker-Enfants Malades; 🇫🇷 Paris, France

Centre de référence des anomalies du développement et syndromes malformatifs de l'Ouest, Hôpital Sud; 🇫🇷 Rennes, France