Figure 1 | Genetics in Medicine

Figure 1

From: Genetic, cell biological, and clinical interrogation of the CFTR mutation c.3700 A>G (p.Ile1234Val) informs strategies for future medical intervention

Figure 1

Qatari siblings with cystic fibrosis transmembrane conductance regulator ( CFTR ) variant c.3700 A>G (predicted to cause the CFTR missense mutation: p.Ile1234Val) exhibit loss of CFTR function in nasal potential difference (NPD) and sweat secretion assays. (a) The original NPD tracing demonstrates absence of any CFTR-mediated response in patient 1 (ΔCl-free+Iso = 1.8 mV) and a relatively borderline CFTR-mediated response (ΔCl-free+Iso = −7.4 mV) in patient 2. Amiloride (Amil.) inhibited the epithelial sodium channel (ENaC), thereby limiting sodium reabsorption and allowing for measurement of the CFTR-mediated chloride response. (b) Evaporimeter tracings from healthy controls (β-adrenergic (β) peak = cholinergic (Chol.) peak), obligate heterozygote (β peak = ½ Chol. peak), and cystic fibrosis (no β peak) are presented to illustrate range of responses with this assay. Tracings from patients 1 and 2 do not show any β-adrenergic response. Short-lived responses following injection of β-adrenergic drugs represent experimental artifact caused by necessary movement of the evaporimeter.

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