# Argininemia: Pathophysiology and Novel Methods for Evaluation of the Disease
## 4 Novel Methods of Evaluation
### Novel Evaluation Methods
#### 4.2.7 Use of New Modeling Methods  
Modelling methods, including knockout mice and induced pluripotent stem cells (iPSCs), have been employed in an attempt to decipher the pathophysiology of the disease.  
Both ARG1-knockout mice, and double ARG1/ARG2-knockout mice have been created by deletion of exon 4 of ARG1 gene, deletion of exon 4 of ARG1 gene and part of exon 4 and 5 of ARG2 gene, and conditional deletion of exons 7 and 8 of ARG1 gene. These mice models replicated multiple features of human arginine, thereby providing new insights in the ARG1-D pathogenesis, revealing for example the implication of guanidino compounds in the emergence of the neurological aberrations of the disorder [50,64,101,102,103,104,105,106,107,108,109,110,111,1112,113]. However, there are still many open questions regarding the exact sequence that leads to the development of arginineia, and therefore new types of knockout mice (such as tissue-selective knockout mice) should be created [23].  
The newest method of modelling diseases could be applied in the context of ARG1-D, namely using appropriately differentiated iPSCs reprogrammed from patients (usually from fibroblasts), that carry the identical genetic information as patients, combined with genome editing technologies to create'repaired' cells that are genetically identical except for the gene mutation site [104,105]. Given the rarity of the disease and the difficulty to obtain an adequate supply of tissue (e.g., liver, blood, brain) from the patients, it is evident that the utilization of such modern modelling methods is of utmost importance [23]. This approach would allow for comparisons at various levels (e.g., cellular, transcriptomic, proteomic, metabolomic) between gene-edited and parental-mutated iPSCs that have been differentiated to hepatocyte-like cells and/or other cell types expressing ARG1 (e.g., neuronal cells) and facilitate the study and discovery of the underlying mechanisms of the disease as well as novel methods for its treatment [23,104,106].  
Table 1 summarises findings from selected studies that propose novel methods of diagnostic evaluations of people with ARG1-D.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Study (First Author,** & **Design/Method** & & \\
**Year of Publication**) & **of Evaluation** & & **Key Findings** \\ \hline \multirow{4}{*}{[PERSON] et al., 2022 [82]} & Genetic database analysis & - & Global birth prevalence of ARG1-D: 2.8 cases/1,000,000 live births. \\  & to establish the prevalence & - & Population prevalence of ARG1-D: 1.4 cases/1,000,000 people. \\  & of ARG1-D & - & 58\% of the alleles responsible for ARG1-D were annotated with \\  & & - & ethnic-specific frequencies. \\  & & - & Birth prevalence rates correlated with demographic characteristics, \\  & & and consanguinity rate of each studied population. \\ \hline \multirow{4}{*}{[PERSON] et al., 2022 [81]} & Use of untargeted & - & An automated computational method was developed that could \\  & metabolomic profiling, & accurately diagnose 16 different IEMs, including arginineia. \\ \cline{1-1}  & and disease-specific & - & The method could serve as a toolset for biological interpretation of \\ \cline{1-1}  & networks to & - & untargeted metabolomics data, improve performance with new case \\ \cline{1-1}  & diagnose IEMs & - & data, and increase the speed and confidence of diagnostic and \\ \hline \multirow{4}{*}{[PERSON] et al., 2021 [29]} & Neurophysiological & - & Neurophysiological methods, such as MEPs, SEPs, F-wave, electromyography, and NCV, could assist in the assessment of a patient with arginineia. \\ \cline{1-1}  & characteristics of a patient & - & In the presented case the only abnormal finding among all performed \\ \cline{1-1}  & with ARG1-D & - & neurophysiological examinations was found in MEPs, where \\ \cline{1-1} \cline{2-1} \cline{2-1} \cline{3-4} \cline{4-4} \cl