SANDO Syndrome

SANDO syndrome are hereditarily heterogeneous mitochondrial diseases that frequently complicate Chronic Progressive External Ophthalmoplegia (CPEO) which is characterized by the gradual paralysis of the external eye muscles. Protheragen is a company with vast experience which offers comprehensive development services for diagnostics and therapeutics of SANDO Syndrome.

Overview of SANDO Syndrome

SANDO Syndrome or Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoparesis is said to be an exceptionally intricate condition that is classified as rare. Even so, it has a great impact on the muscular and nervous systems. Cases suffering from SANDO syndrome show symptoms of ophthalmoplegia, ataxia, and dysarthria which all portray sensory dysfunction. Most cases show symptoms of this disorder in adulthood and it, unfortunately, gets worse with time. Mutations to the POLG gene causes dysfunctional expression of the DNA polymerase gamma enzyme which serves as the primary rationale behind this syndrome. This enzyme, regarded as the guardian of mitochondrial DNA, becomes dysfunctional and leads to deletions of the mitochondrial DNA which in turn causes impairment in high energy performing muscles and neuronal tissues.

Fig.1 Diagnostic genetic algorithms including SANDO syndrome. (Kierdaszuk B., et al., 2020)

Diagnostics Development for SANDO Syndrome

• Genetic Testing and Sequencing
  Identifying the mutations in the POLG gene is the primary objective of molecular diagnostics pertaining to SANDO Syndrome. Next generation sequencing NGS has enabled the detection of these mutations with great detail. Pathogenic variants in POLG are usually detected by whole exome sequencing WES or by targeted gene panels.
• Functional Assays
  Beyond sequencing the DNA, functional assays are required to assess the consequences of POLG mutations on mitochondrial physiology. qPCR and Southern blotting are techniques used to determine the mitochondrial genome copy number and deletion rate. These methods reveal the scope of mitochondrial dysfunction and assist in the genetic findings.
• Biomarker Identification
  The latest trends in the molecular diagnostics is that of searching for biomarkers which can contribute towards early detection of a problem and subsequent monitoring of its progression. For example, metabolomic profiling has shown specific metabolic signatures that might indicate mitochondrial dysfunction relevant to SANDO Syndrome.

Therapeutics Development for SANDO Syndrome

Our Services

Protheragen offers comprehensive services for the development of diagnostics and therapeutics for SANDO Syndrome. Our expertise in molecular diagnostics includes advanced genetic testing and functional assays to identify and characterize POLG mutations. In the realm of therapeutics, Protheragen leverages cutting-edge research to develop innovative therapeutics for SANDO Syndrome. Our services encompass the design and implementation of preclinical studies, gene therapy development, and the evaluation of therapeutics.

SANDO Syndrome Target Validation & Pathway Analysis Services

Protheragen offers comprehensive target validation services to identify and prioritize druggable targets for SANDO syndrome, focusing on pathways directly linked to POLG1 dysfunction and mtDNA instability. Our team performs systematic pathway profiling to characterize defects in mtDNA replication, repair, and maintenance; OXPHOS complex assembly and activity; mitochondrial biogenesis; redox balance; and apoptotic signaling in SANDO-relevant cell types. We use quantitative PCR (qPCR), digital PCR (dPCR), and next-generation sequencing (NGS) to measure mtDNA copy number, deletion frequency, and heteroplasmy levels, alongside Western blotting and immunofluorescence to assess expression and localization of Polγ, mitochondrial transcription factors, and respiratory chain subunits.

Custom SANDO Syndrome Cellular Model Development Services

Highly predictive cellular models are foundational for SANDO syndrome preclinical research, and Protheragen specializes in creating patient-relevant, genetically defined in vitro systems. Our model development services include:

• Patient-derived iPSC differentiation: Generation of iPSC lines from SANDO syndrome patients with confirmed POLG1 mutations, followed by directed differentiation into retinal ganglion cells (RGCs), dorsal root ganglion (DRG) sensory neurons, cerebellar neurons, and skeletal myotubes—key cell types affected in the disease.
• Isogenic control models: CRISPR-Cas9 correction of POLG1 mutations in patient iPSCs to create genetically matched control lines, enabling precise attribution of phenotypic changes to the disease-causing mutation.
• Gene-edited disease models: Engineering of POLG1 pathogenic mutations (e.g., p.Ala467Thr, p.Arg627Gln) into wild-type human iPSCs or immortalized cell lines to generate scalable, standardized SANDO syndrome models for high-throughput applications.

High-Throughput Screening (HTS) Services for SANDO Therapeutics

Protheragen provides customized high-throughput screening services to identify novel small molecules, biologics, or mitochondrial-targeted agents with therapeutic potential for SANDO syndrome. Our screening platforms are optimized for mitochondrial and neuro-ocular endpoints, compatible with large compound libraries, and compatible with patient-derived SANDO cellular models. Key screening assays include:

• Mitochondrial bioenergetics screening: Quantitative measurement of ATP production, oxygen consumption rate (OCR), and extracellular acidification rate (ECAR) to identify compounds that restore respiratory chain function in POLG1-mutant cells.
• mtDNA stability screening: Fluorescent and PCR-based assays to detect increases in mtDNA copy number, reduction in mtDNA deletions, or improved mtDNA integrity following compound treatment.
• ROS reduction screening: Fluorometric probes for intracellular ROS, mitochondrial superoxide, and lipid peroxidation to identify antioxidants and redox-modulating agents.
• Neuroprotective screening: Assays for RGC and sensory neuron survival, neurite length, and synaptic integrity to identify candidates that prevent SANDO-related neurodegeneration.

In Vitro Efficacy & Mechanism of Action (MoA) Assessment Services

For advanced lead candidates, Protheragen provides detailed in vitro efficacy and MoA characterization to define therapeutic potential and molecular function in SANDO syndrome models. Our comprehensive efficacy profiling includes:

• Mitochondrial functional rescue: Quantification of OXPHOS complex activity, mitochondrial membrane potential, mitochondrial mass, and mitophagy flux using flow cytometry, confocal microscopy, and biochemical assays.
• mtDNA maintenance evaluation: Long-term culture studies to assess sustained improvement in mtDNA copy number, reduced mutation accumulation, and restored Polγ activity.
• Neuronal and ocular function recovery: Analysis of RGC action potential firing, sensory neuron calcium signaling, and myotube contractility to demonstrate functional rescue of SANDO-affected cell types.
• Pathway modulation: Phosphoproteomics, transcriptomics, and metabolomics to define downstream signaling pathways activated or normalized by therapeutic candidates.

Preclinical Safety & Toxicology Screening Services

Protheragen delivers targeted in vitro safety profiling to identify potential off-target effects of SANDO syndrome therapeutic candidates, with a focus on mitochondrial and neural safety. Our safety services include:

• Mitochondrial toxicity screening: Assessment of effects on wild-type mitochondrial function, mtDNA integrity, and cellular bioenergetics to avoid exacerbating mitochondrial dysfunction.
• Neuronal and ocular cytotoxicity: Evaluation of cell viability, apoptosis, and morphological integrity in healthy RGCs, sensory neurons, and brain microvascular endothelial cells.
• Genetic safety assessment: Analysis of nuclear DNA damage, chromosomal stability, and off-target mtDNA effects to ensure genomic safety.
• Cytotoxicity and IC50 determination: Dose-range finding studies to establish therapeutic windows and identify safe concentrations for preclinical advancement.

Diagnostics Development

• Karyotype Analysis Service
• Omics Analysis Service
• Biomarker Development Service
• Artificial Intelligence Service

Therapeutic Development

• Small Molecule Drug
• Cell Therapy
• Gene Therapy
• Therapeutic Antibody
• Therapeutic Peptide
• Therapeutic Protein

Preclinical Research

• Pharmacodynamics Study Services
• Pharmacokinetics Study Services
• Drug Safety Evaluation Services

Disease Models

• POLG Mutant Mouse Models
• Ethidium Bromide-Induced Mitochondrial DNA Depletion Models
• POLG Knockdown Zebrafish Models
• POLG Mutant Canine Models

Protheragen specializes in creating relevant in vitro and in vivo models of SANDO Syndrome. Cell lines harboring POLG mutations and animal models recapitulating the disease phenotype are used to study pathogenic mechanisms and test therapeutic candidates. These models provide valuable insights into disease progression and therapeutic efficacy. If you are interested in our services, please feel free to contact us.

References

• Kierdaszuk, Biruta, et al. "Progressive External Ophthalmoplegia in Polish Patients—From Clinical Evaluation to Genetic Confirmation." Genes 12.1 (2020): 54.
• Bandettini di Poggio, Monica, et al. "Dopamine-agonist responsive Parkinsonism in a patient with the SANDO syndrome caused by POLG mutation." BMC medical genetics 14 (2013): 1-4.
• Lovan, Alyson, Ihtsham ul Haq, and Nikhil Balakrishnan. "Diagnostic challenges in movement disorders: Sensory Ataxia Neuropathy Dysarthria and Ophthalmoplegia (SANDO) syndrome." Case Reports 2013 (2013): bcr2013010343.