NIPD on cffDNA for Triplet Repeat Diseases

Comparison of Two NGS Phasing Techniques of Parental Haplotypes for NIPD of Triplet Expansion Diseases


Lead Sponsor: University Hospital, Montpellier

Collaborator: Agence de La Biomédecine

Source University Hospital, Montpellier
Brief Summary

The purprose of this study is to develop and validate an analytical NIPD test for triplet repeat disesases by NGS analysis from maternal blood, searching for the familial mutation in families at risk of having one of the following triplet repeat diseases: Huntington's disease, Myotonic dystrophy, Fragile X syndrome.. A comparison of two 3rd generation long fragment DNA sequencing techniques will be performed. These methods are based of the phasing techniques of parental haplotypes without the proband.

Detailed Description

Context: The ability to sequence fetal cfDNA has led to exciting new developments for the non-invasive genetic diagnosis of monogenic diseases (DPNI_MGR). Various tests are proposed for diseases with predominantly de novo dominant, dominant paternal and some recessive paternal mutations. However, technical difficulties related to the determination of the maternal allelic balance remain, in particular during the phasing of parental haplotypes according to a trio strategy which requires the availability of parental genomic DNAs and at least one healthy or affected child. Moreover 2nd generation sequencers do not allow the haplotyping of alleles carrying dynamic mutations. Objectives: This project proposes the validation of a semi-universal DPNI_MGR test applicable to the majority of the genes and mutations involved in DPN requests from phasing of parental haplotypes by 3rd generation long-fragment DNA sequencing techniques coupled with targeted sequencing of free circulating DNA from maternal plasma. This test will be validated using triplet expansion diseases, which are the second indication of DPN at the national level. Methodology : Retrospective study of 16 couples at risk of transmitting a disease with triplet expansions (Myotonic dystrophy of Steinert, Huntington's disease, FRAXA, SCA1, 2, 3) Phase 1 : - Determination for 8 pairs of parental haplotypes according to the technique "Nanopore Cas9 Targeted-Sequencing" (nCATS) and validation of the analytical parameters and quality of this method (coverage rate of the regions of interest, error rate, identification of the morbid allele carrying the expansion ...), - Comparison of the parental haplotypes obtained in "Nanopore" technique versus those obtained by the "Linked Reads 10xGenomics" technique in these same 8 pairs (the sequencing and phasing data by this 2nd approach are available from a previous study), - Evaluation of the concordance of the fetal genotype results obtained during the standard examination (DPN by amniocentesis or choriocentesis) and those obtained with these new approaches of phasing in PNID. Phase 2: - Validation of the best performing workflow (efficiency / cost) of phase 1 over 8 additional pairs for a clinical transfer of the approach. Expected results and prospects: This study should make it possible to define the best performing test for the DPNI of triplet expansion diseases in accordance with the knowledge of the art and to validate the transfer conditions in clinical practice of the approach (equipment, reagents, cost analysis, analytical validation criteria ....). The validated workflow should be as universal as possible to secondarily provide national level access to a wide range of rare diseases NIDP by future adjustments of the gene content of the free circulating DNA sequencing panels.

Overall Status Active, not recruiting
Start Date September 1, 2020
Completion Date December 1, 2023
Primary Completion Date September 1, 2023
Study Type Observational
Primary Outcome
Measure Time Frame
Concordance rate between cell free foetal DNA based genetic 36 months
Secondary Outcome
Measure Time Frame
Qualitative process to define the differents steps to analysis of the cell free foetal DNA 36 months
Enrollment 36

Intervention Type: Genetic

Intervention Name: Non invasive prenatal diagnosis

Description: Search for the familial mutation involved in DPN requests from phasing of parental haplotypes by 3rd generation long-fragment DNA sequencing techniques coupled with targeted sequencing of free circulating DNA from maternal plasma.

Arm Group Label: 16 pregnant women and their spouses


Sampling Method: Non-Probability Sample


Inclusion criteria: - Couple at risk (based on family history or echographic findings) for one of the following diseases: Huntington's disease, Steinert's myotonic dystrophy, fragile X - Written informed consent was obtained for DIACCIMEX study and mentionned "authorization for use for further studies on familial pathology. Indeed, the DNA can be used anonymized for the development of new analyzes of non-invasive prenatal diagnosis". - Prenatal diagnosis has been done for the pregnancy during which maternal blood has been collected - Couple molecular diagnosis results for one of the following diseases (Huntington's disease, Steinert's myotonic dystrophy, fragile X and spinocerebellar ataxias 1, 2 or 3 ) MUST BE AVAILABLE. Exclusion criteria: - Couple Genomic DNA are unavailable - Subjects at risk of transmitting the family disease, but not wishing to know their molecular status - Individuals under guardianship by court order

Gender: All

Minimum Age: 18 Months

Maximum Age: N/A

Healthy Volunteers: No

Overall Official
Last Name Role Affiliation
Marie Claire VINCENT, PhD-PharmaD Principal Investigator University Hospital, Montpellier
Facility: CHU Montpellier
Location Countries


Verification Date

September 2020

Responsible Party

Type: Sponsor

Has Expanded Access No
Condition Browse
Arm Group

Label: 16 pregnant women and their spouses

Description: 16 pregnant women and their spouses

Patient Data Undecided
Study Design Info

Observational Model: Cohort

Time Perspective: Retrospective